> "There's a general phenomenon I've noticed on the internet. Any forum with free speech and little to no moderation becomes right wing. Leftist ideas cannot exist without censorship and moderation."

I suspect that "right wing" here is euphemism for more of sexism and racism. Because I can tell you that moderate conservative, economic conservative and for that matter libertarian forums all have moderation too. They cant exist without moderation and censorship either.

What happens however is that without moderation people will use harassment, trolling, both including massive sexist and racist statements to push away people who disagree with them. And people who dont want to be subjects of those leave. So you end up with people who are fine with trolling, racism and sexism and the end result is biased toward right wing. You know who will be harassed the most? Anyone perceived as feminist or sjw.

The actual extreme left, which I guess would be defined more as a marxism or communists, is relatively small in numbers. They are also pretty often sexists and racists too, so I dunno how it crosses with that.