there really is a substantial fraction of what self-identifies as the "social justice" movement, primarily in an online context, that really is toxic, and that the rest of the left and the serious, sane part of the SJers aren't doing enough to call them out on it
Minus the online bit, this is fully generalizable against any political group, (and a lot of non-political groups as well). Which groups do you choose to lambast for "not calling out toxic members of that group"? Presumably the groups that you don't like. This is the art of politics.
"I don't have a problem with X group, but you have to agree that the subset Y of them are really horrible so lets continue to talk about how horrible they are" is Dark Arts to the max.
Which groups do you choose to lambast for "not calling out toxic members of that group"? Presumably the groups that you don't like.
This is a accurate description of a common political behavior.
But recognizing this doesn't mean that all groups must actually have symmetrically malign subgroups, or that the mainstream in every group has the same relationship towards these subgroups. You can support the mainstream positions of both group A and group B, but be more critical of group B due to the existence of a subgroup you consider malign.
What is something you used to believe, preferably something concrete with direct or implied predictions, that you now know was dead wrong. Was your belief rational given what you knew and could know back then, or was it irrational, and why?
Edit: I feel like some of these are getting a bit glib and political. Please try to explain what false assumptions or biases were underlying your beliefs - be introspective - this is LW after all.