It's far worse than that: after leaving they continue to talk about us, as someone might do for an unfaithful ex, trashing our reputation. We can be toxic AF here, with little to no warning labels about which spaces have what echo chamber policies in place; only people with extraordinarily thick skins can stand this space, especially for long periods of time.

I don't quite agree. The people that leave silently (the overwhelimingly large majority) don't leave as an active decision, but rather fail to come back because there isn't enough interest (or nagging notifications).

And for people to realize their overton window is scewed to the right it is sufficient to be exposed to left wing ideas, no need to find them reasonable. The regular existence of these ideas in discourse is sufficient.

just because you lean left it doesn't mean you are left. It means your ass is still squarely in the center. Being "Leftist" is to have the tacit understanding that the far right means to eradicate progressive thought by any means necessary, and that any threats of violence from "our" side are spoken from a place of self defence. The right does not want "discussion" to lead to compromise, they want it to lead to compliance. Besides, we've "been having the discussion" since the 1970's and as every hostage negotiator knows: if you keep them talking, they aren't acting. It's a stalling tactic.