A person with lots of integrity wont change what they say easily. If they don't believe that there are more than two genders, then for them to use a third pronoun with a straight face they would have to rebuild their entire worldview around gender. Of course that would be a good thing, but doing that would take a lot of work and not something you can get them to do in the few seconds it takes for a conversation to get awkward.

I'd be more wary of the people with low integrity who just say what others want to hear, they change their speech but doesn't actually change their behavior and will still discriminate and undermine groups even when forced to change their speech pattern.

Stallman seems to me like a person with an extremely high level of integrity, if a normal person believe that voluntary pedophilia is fine they would just shut up and join the mob but not Stallman. He faced his world view head on and no longer believe that pedophilia is fine, and we can be pretty sure that he actually changed since he doesn't buckle to pressure. The same can not be said about most politicians and other conventional leaders.