Sigh.  The dynamic does not work the way that many people think it does.

In a culturally-mixed environment, confidently believing that you represent an overwhelming ideological majority…or, at least, acting like you represent an overwhelming ideological majority, which usually amounts to the same thing…is kind of a superpower. 

Many people are very happy to talk about potentially-charged subjects with their trusted allies.  Many fewer people are happy to talk about potentially-charged subjects with those who disagree with them.  And even if you’re the sort of bellicose person who’s happy to do that second thing, you probably want to build up to it; you want to do it when you have a lot of energy and mental clarity, when all your arguments are lined up in your head, etc.  This isn’t a factional trait, it applies to most of everyone. 

If you think that everyone around you is probably an ally, you’re likely to go ahead and start blithely talking about those potentially-charged subjects.  Your actual allies will happily talk back.  Everyone else will probably get quiet, not wanting to have the kind of discussion that’s actually a conflict.

This doesn’t need to iterate that many times before you’ve established a tacit-but-clear norm of “these people are allowed to say their piece in this space, but those people definitely have to shut up and suppress their thoughts.”  And it was accomplished without intentional action from anyone, without anyone understanding what happened. 

Hell, this works even if the talkers are very much in the minority with regard to their opinions, so long as they’re too dense to realize it.