I'm skeptical that there exists any leftist mainstream place that isn't actually a right-wing place disguised as leftist.

I'm also skeptical that all of those loud but irrational voices are genuine. Especially given Russia's MO for online trolling where they push both sides of any issue to extremes to sow division. Not to say that I believe everyone on the left is rational and reasonable. But why would the tone be so different between "mainstream" and "non-mainstream" left places if the position you're talking about is as ubiquitous to the left as you claim it is?