There is nothing immature about so-called "foul" language, and there's nothing mature about refraining from using such language.
Curse words are verbal tools, used to reflect extremities of emotion. Like any tool, they are appropriate for some situations and not others, and over-use of them can cause the blade to be dulled.
And "Goddamn" is so common that it hardly even counts as any more of a curse word than does "golly" -- which, by the way, originally meant, "God's body," and was considered an obscenity.
Handguns and assault rifles are literal tools, used for the purposes of killing people, and I think it's a very mature decision to refrain from using those.
To begin with, it is absolutely
absurd to equate the use of a "vulgar" word -- which endangers nobody -- with the intentional discharge of a firearm against a victim.
Knowing when and when not to use a "curse" word is a sign of maturity and respect, certainly. There's nothing mature about using a "vulgar" word in a professional setting, for instance, when you know it is likely to cause offense or to be seen as rudely emotional.
But, similarly, there's nothing
immature about using them amongst people whom you know will not take offense, or in your own mind. (Which, we should all bear in mind, is where Archer used the "f-word" in
Last Full Measure: In his internal monologue.)
I think it's pretty presumptuous to say that refraining from using curses is a sign of an immature person;
Then it's a good thing I never said that.
Specifically, I said that refraining from using a "vulgar" word is not inherently a sign of maturity; I never said it was a sign of immaturity.
Some would argue that a more mature society wouldn't get too bothered by the fact that certain words are derived from Anglo-Saxon rather than Latin.
Some would argue that to describe a society as "more mature" is
profoundly ethnocentric, and that it's not at all hard to see where someone from another society might be deeply insulted by the implication that his/her society isn't "mature."
And if we were talking about
real societies, that would be a completely valid point. But
Christopher is talking about a fictional society being, in theory, more "mature" than modern society, so I doubt any reasonable person is going to be too offended.
Having said that, I've often felt that the Federation is more than a little ethnocentric (or, if you well, "Federation-centric") in its thinking and evaluation of other cultures, and more than a little self-congratulatory about its supposedly greater levels of "social maturity" than its ancestors' so-called "primitive" societies.