People are not fringe will tend to abandon sites that embrace people who are, even tacitly. Sites that create havens for them will naturally tend to become sites that consist almost solely of them.
Any violent thug can go spread their message in the town streets as long as they're not causing a disturbance. It doesn't happen very much, because it requires effort and it's sure to attract opposition. That opposition is necessary, like anti-bodies attacking an invading bacteria. By shutting out the harmful bacteria where anti-bodies can't reach them, they'll do nothing but grow and fester.
Are you saying that if person X goes out and starts calling for mass shootings to rid the world of Y, that they wouldn't be arrested?
Very few people actually want such a site arrangement. Believe it or not, I have no interest in interfacing with people who want to kill me unless they are open to honest and rational debate, which few are. One of the reasons I enjoy Hacker News is because I know won't have to deal with the type of people that will frequent the fringe elements of the style of site you are advocating for.
Also, I'd hardly call a business led moratorium on speech advocating terrorism and genocide "moving towards Orwellian style censorship". Absolutely nothing is stopping these individuals from standing up their own server and hosting this content themselves. They aren't banned by an ISP. Moreover, business owners should be allowed to express their opinions too, including who to do business with.
I’m not really in favor of what CloudFlare’s done here, but it’s really a fact of basic statistics that exposing the mainstream to well-made propaganda is far more dangerous than exposing radicals to the mainstream.
Imagine 1% of non-radicalized people exposed to radicalism become dangerous and 50% of radicalized people are de-radicalized by exposure to the mainstream (laughably optimistic). If you start with 100 million non-radicals and 500 thousand radicals, you have a 125% increase in radicalization.
This is how we now have so many flat earthers. When you have massive reach, it’s easy to grow your numbers.