Self-censorship is a norm which always existed as a social behavior, even online. In a small geeky world of early days of Internet, when community of connected people was small and more homogeneous, it was easier to touch certain topics without receiving strong reactions, but it didn’t mean self-censorship did not exist. It just concerned different things and the worst that could happen was a ban on the forum or IRC channel. It’s still the case for unimportant people: no one cares what random Joe says online. Everyone expects that opinion leader conforms to the norms of society - hence all those crazy scientists are being ostracized for spreading nonsense outside their field of research.

Phpbb forums didn't go away because of self censorship, they were simply replaced with bigger sites like Reddit. If you're trying to create a community around a niche topic, a subreddit is substantially easier to create than deploying and maintaining a forum.

I think what is perceived by a community as right or wrong changes as the composition of the community changes...I mean Trump doesn't self-censor because he reflects the values of his broader base and his base eats up whatever he says....RMS' hugs and kisses, free love, anything goes attitude might have been ok during the hippie era of the 70s and 80s during the formative years of his career but does not reflect the values and sensibilities of today's broader development community....which means he needed to adapt or step down. -- The Dark knight quote - "You either die a hero or live long enough to see yourself become a villain" seems apt in this scenario.