I'm coming to this thread late, and I'm impressed, lots of good discussion and points here.

Something I'll add that I see frequently from libs is this type of argument (strawman maybe?) used to push back against anyone to their left. It's presenting a bad faith narrative that there is actually some significant population of people who identify as leftist and are actually secretly reactionary because of some perceived gotcha they concoct. It's kind of hard to explain, but I know it when I hear it.

Examples of things I've heard in my own life: "well of course I support Palestinian rights, but I know at least some of those people are only critical of Israel because they are antisemitic, how can I take their arguments seriously?"

"Bernie seems like a good guy, but have you seen those ads, no diversity. I'm sure there are a lot of people who like him who are actually racist"

I feel like this fits neatly into this category, even if I'm not doing a good job of explaining it.