That's rather off the mark, though, to say they were "made up". Much of what was created was inspired and formed by teachings in Catholicism. I guess on that level you can say they were "made up".
It's true that there is a sort of ignorance on the part of some as to the origins of some holidays, but to say that they just "obey their preachers and complain because Christmas is commercialized" betrays a certain lack of information about these Protestant denominations. I hope it isn't a prejudice against them. Since I am no authority on the Reformation, I can't really speak in any great detail. I can only speak as one of those Protestants from all my life. Speaking of what I have witnessed being done.
The originaters of most of the younger Protestant churches weren't trained by the older churches. They built their religions by reading the Bible. This was, for most part, on purpose, they were rejecting the other teachings of the older churches.
They rejected the idea that much of Christianity wasn't written in the bible but passed on directly. They rejected the idea that the practices and rituals of the other churches were intrinsic to Christianity. The founders never learned those practices and teachings, they weren't trained priests or monks.
They did create new religions from scratch, based in part on outside observation of primarily Catholic practices.
They have every right to call themselves Christian, they have every right to call what they have religion, but no, it has no basis beyond anything you or I could make up on the spot right now by picking up a bible and preaching on a street corner.
I think it's absurd for these denominations to have an opinion on Christmas that should be given any weight. They don't have Mass, Christmas really has no more to do with them than it does to an atheist who puts up a tree and puts presents under it.
Easter is "holy day" for a reason. Christmas isn't holy. It's celebrated just because it was a popular festival and the early church wanted to absorb the common folk. There's a big difference there. It's especially farcical to criticize commercialization and secularization of Christmas considering it was created by the early church purely for "commercial" reasons to begin with.
And I'm sorry if I'm coming across that younger Protestant religions aren't "real" or whatever, I'm really not trying to say that.
1. Which "younger Protestant denominations" do you have in mind?
The Reformers of the first several generations were very much "trained by the older churches." The evangelical Reformed churches,
to this very day use confessions and theologies from the 16th and 17th centuries. The SBC was founded in the 19th century, by churches each of which held to the Second London Baptist Confession of 1689, which is drawn from the Savoy Confession and the Westminster Confession. Both Reformed Baptists and Presbyterians today are widely influenced by theologians like Francis Turretin. Turretin was deeply immersed in the Western tradition. One can even trace the history of Westiminster Seminary back to the days of Jonathan Edwards. We also have well known Patristics scholars among us. The same can be said of the Lutherans, even the evangelical Anglicans.
2. They rejected the idea that much of Christianity wasn't written in the bible but passed on directly.
No, they rejected the idea that doctrine and practice is infallibly rooted in both Scripture and tradition. At the time, the Catholic Church's rule of faith was Partim-Partim. The Protestants to which you seem to be referring rejected that in favor of Sola Scriptura. Sola Scriptura does not reject tradition qua tradition. It merely rejects the infallibility of tradition. That view grew up right alongside Partim-Partim for many centuries until the split of the Reformation. They came to reject seven sacraments over only two, for example, insofar as only two are to be found in Scripture. However, they did not reject notions such as marriage, funerals, the role of elders, etc. I'd also point out that for such items as justification - there were many views of justification in the Western Church at the time of the Reformation, because the Western Church had not (infallibly) determined a particular view. Trent ensconced one against the Protestants. Justification by faith alone is a doctrine to be found in "tradition" as well as Scripture for that reason. So, what you say is inaccurate. Protestantism's rule of faith is far more nuanced.
The founders never learned those practices and teachings, they weren't trained priests or monks.
Luther, Calvin, Zwingli, Cranmer, to name just a few - they weren't trained priests or monks? Where did you get that idea?
If that's what you think about the Reformers, the Reformation, the High Orthodox era of Protestantism, and Protestant doctrinal thought,then I strongly suggest you take a gander at Post-Reformation Reformed Dogmatics by Richard Muller. It documents exactly the reverse of your statements here.
I think it's absurd for these denominations to have an opinion on Christmas that should be given any weight. They don't have Mass, Christmas really has no more to do with them than it does to an atheist who puts up a tree and puts presents under it.
3. On the one hand there's a certain level of truth there. Christmas is a Romanist holy day. However, on the other, Protestants are free to practice it if they so choose. So, why shouldn't they be allowed to have a religious opinion of it that has no weight at all?
It's celebrated just because it was a popular festival and the early church wanted to absorb the common folk. There's a big difference there. It's especially farcical to criticize commercialization and secularization of Christmas considering it was created by the early church purely for "commercial" reasons to begin with.
Actually, the reason for the choice of December 25 is not known.
The December 25 date was chosen for multiple (and sometimes unknown) reasons, and it was adopted in different places at different times. It's misleading to claim that "the Emperor Constantine chose the date" or "the Catholic Church chose December 25th," or it was chosen for "commercial reasons."
Joseph Kelly writes:
"In 274 Aurelian [a Roman emperor] instituted the cult of Sol Invictus, the Unconquered Sun....Aurelian made December 25, the winter solstice, the birthday of Sol Invictus and thus a major feast day throughout the Roman Empire....In 336 the local church at Rome proclaimed December 25 as the dies natalis Christi, 'the natal day of Christ,' that is, his birthday. The document which says this does not justify or explain it. It merely says that this is the day, that is, the date had been accepted by the Roman church some time before and since everyone knew about it, discussion of the date was not necessary. But how long before 336 was the date for Christmas accepted? Historians have wondered whether the Christians in the late third century had waged a propaganda war against Aurelian, promoting their Sun of Righteousness [Jesus in the context of Malachi 4:2], the Sol Iustitiae against his Unconquered Sun, the Sol Invictus....We should also recall that Sextus Julius Africanus [a Christian who wrote during the first half of the third century] had already proposed December 25 as the date of Christ's birth. Aurelian's opponents may have plausibly reasoned that if the date already existed [in Christian circles], why not use it against the imperial cult of the Sun?...The second piece of evidence for a third-century propaganda struggle is a work of art, a mosaic on the ceiling of a tomb of the family Julii and now preserved in the necropolis (Greek for 'city of the dead') under St. Peter's basilica in Rome. It portrays Christ driving a chariot through the heavens, just as the pagan sun god Helios did, and Jesus, like the god, has rays of light emanating from his head....They date the mosaic to the late third century, that is, at the time when the emperor Aurelian was promoting the cult of the Unconquered Sun. Significantly, this is the only ancient portrayal of Christ as the sun. Historians find it impossible to believe that this portrayal was just coincidentally produced in the city of Rome at the very time when the pagans were promoting the cult of their sun." (The Origins Of Christmas [Collegeville, Minnesota: Liturgical Press, 2004], pp. 65-68)
William Tighe:
"Rather, the pagan festival of the 'Birth of the Unconquered Son' instituted by the Roman Emperor Aurelian on 25 December 274, was almost certainly an attempt to create a pagan alternative to a date that was already of some significance to Roman Christians. Thus the 'pagan origins of Christmas' is a myth without historical substance....Thus, December 25th as the date of the Christ’s birth appears to owe nothing whatsoever to pagan influences upon the practice of the Church during or after Constantine’s time. It is wholly unlikely to have been the actual date of Christ’s birth, but it arose entirely from the efforts of early Latin Christians to determine the historical date of Christ’s death. And the pagan feast which the Emperor Aurelian instituted on that date in the year 274 was not only an effort to use the winter solstice to make a political statement, but also almost certainly an attempt to give a pagan significance to a date already of importance to Roman Christians. The Christians, in turn, could at a later date re-appropriate the pagan 'Birth of the Unconquered Sun' to refer, on the occasion of the birth of Christ, to the rising of the 'Sun of Salvation' or the 'Sun of Justice.'"
Also:
"St. Augustine observes somethere that the Donatists 'differ from us' in not observing the day [January 6], which was not the case with regard to 25 December, and which in turn implies that 25 December was a 'liturgically significant day' before the Catholic/Donatist split of 310 and onwards."
Others have different reasons. I celebrate the historical continuity of an ancient holiday that is a connecting thread through the ages to the beginnings of Human civilization.
Hardly. False decretals...popes and antipopes! Where is the evidence for the Marian dogmas, papal succession, and prayers to the saints, and that's just for starters - going back to the beginning of Christianity? It's hard to trace an "unbroken line" of theology, let's say for justification by infused merit alone, when we can find justification by faith alone in the Early Church Fathers and Rome had no defined position on justification until the Council of Trent Indeed, how did the early church get along without a canon of Scripture until Trent? Where's the Roman Catholic canon before then? 
