The reason for the lack of "openness" is that a huge amount of the, as you call it, "dissenting opinion" for the newest Star Trek films is 1) unsolicited 2) repetitive 3) not particularly thoughtful.
I hate to use a political analogy, but it's sort of like the Benghazi hearings. It MIGHT have been a legitimate issue the first time, possibly even the second time. But eight congressional hearings and fifty four press releases later, it has become obvious that one political party is trying REALLY HARD to find something to be mad about, and they want everyone else to be mad about it too, and they become upset and even offended when others refrain from partaking of their outrage.
There are, of course, legitimate criticisms of STXI and STID. The pace of both movies was very rushed, and character development for Carol Marcus and Nero both suffered from choppy editing. Kirk's rise to command, while excusable for dramatic reasons, feels more than a little contrived in hindsight, and the "caught in Earth's gravity" scene qualifies as gratuitous and shameful abuse of the Rule of Cool. These are legitimate criticisms.
"It sucks because it violates teh canon!" is not really a legitimate criticism. It is, however, the basis of the majority of such criticisms, which is one of the reasons most of the fans continue to roll their eyes at the critics who make those kinds of statements.
