I think Vulcan society is in some ways VERY problematic, since even if they are a democracy they seem to enforce a level of conformity that shuns and stigmatizes anyone that doesn’t fit their mold of dispassionate logic.
I mean, yes and no? I think it's clear that there's a diversity of traditions within Vulcan society over how to interpret Surak's teachings and how to implement them.
Especially, given that we know how Sarek “felt” about things in his life from Picard’s mind meld, what is the difference between Vulcan suppression of their feelings, with what seems to be a society wide enforcement of that standard, and a societal order that teaches people to suppress their sexual orientation?
I think the difference is that one is suppressing a naturally-occurring minority group and the other is not.
I would interpret the Vulcans as not caring about sexual orientation per se. If you were born LGBT, I doubt they care. If you enter pon farr and you have an irresistible need to mate with someone of your own gender, I imagine the Vulcans treat it the same way they treat a heterosexual in the same situation: lots of shame around the fact that it's uncontrolled emotion, not shame over who the emotion is directed at. What scandalizes them is not the
homo- part of "homosexuality," it's the -
sexuality part.
From a Federation POV, I imagine their general attitude is, "As long as you don't violate the fundamental constitutional rights of your minority groups, we can accept that your species may require a level of conformity for its survival that we otherwise might not tolerate."
Given that there are
v'tosh ka'tur, and given that later on we know the Romulan nation re-settles on Vulcan and is not forced to adopt orthodox Surakism, I suspect Vulcan doesn't engage in overt discrimination against non-Surakian minorities.
That and bonding a child to marriage and fights to the death over mates.
And then the Federation is like, "Wait, do you actually force them to marry against their will as adults? No? And everyone knows what they're entering into with this ritual combat and it occurs on the basis of consent? Yeah? Okay, that's fine then."
Possibly problematic from a Human standpoint, but not oppressive of fundamental rights.