Case in point, alt-left communities who champion "free speech" like Hacker News often shadowban people who express opinions they disagree with, especially if it's said in the wrong 'tone' of voice--direct aggression rather than passive aggressiveness, which is the preferred atmosphere here.
I'm always suspicious when specifically “left” or “right” or any other specific political colors are mentioned as such with regards to censorship — it reeks of not being objective.
It is a problem of all mankind, not any particular political color; the only color above it are of course specifically the free speech advocates.