In the past and in the present endorsing certain ideas would make people less likely to want to associate with you. The mix of ideas that will make people less likely to want to associate with you has changed, and as such the need to self-police is falling on populations that haven't felt it before, but we'd have to really get into the weeds to work out if the number of "off limits for polite society" topics has really grown.

Some things that have changed. First, many social interactions have shifted to the online space, and we've failed miserably to provide a public square online. There mostly isn't one, only the online equivalent to shopping malls and private clubs (albeit with permissive entrance requirements). These shopping malls and private clubs have become so ubiquitous that only people with opinions too extreme for them are looking for alternatives. As a result, the few public spaces that somehow pop up in the cracks become the host of concentrated extreme speech, which is not really a viable foundation for a community.

Second, the current online platforms record everything posted on them in perpetuity. Many of them make this content infinitely searchable. To some extent this is just the nature of digital communications, they are inherently easy to archive. So, us smallfolk have lost the benefit of ephemeral communications. This is a big deal -- I think lots of us who grew up in the pre-internet era have some memory of saying something that's in retrospect pretty embarrassing, but is now lost to time.

It is one thing to say something in front of friends and get called out by people you have real relationships with, and another thing entirely to fall under the wrath of the open internet. In fact, I think this is quite bad for public discourse, as a number of people have just been shamed into silence, and others have figured "I've been banished by everyone but the bigots at this point, may as well fit in with them."

Finally, most of the platforms optimize for engagement. Extreme opinions drive engagement. Can you imagine a club where the proprietor placed microphones on every table, selected conversations to amplify? Ok, now imagine the proprietor has a very poor grasp of the local language, and mostly evaluates which conversations are interesting by how large a crowd they've already drawn and how loud the argument is. That's the environment that most online discussions take place in.

It wouldn't be that surprising for a large number of the patrons to ask for strict admissions requirements. The only surprising thing is that we put up with this bizarre business model in the first place. Ah but the drink are free since the whole affair is sponsored by companies and foreign intelligence agencies. All the paid clubs couldn't compete with free.