Sure, but why do we have to conflate "disagreement" with "undesirability"? I'm old enough to remember a time when we could disagree about things without pretending our opponents are Hitler reincarnate. I often find myself wanting to spend more time with people I disagree with to understand their perspectives better or to help them see that we probably have more common ground than they may realize or even just to do my part to heal our culture by rejecting the notion that it's necessary, good, or morally acceptable to hate people we disagree with.

The irony is that the original antifa - https://en.wikipedia.org/wiki/Antifaschistische_Aktion - was, essentially, a KPD-affiliated militia. As such, their definition of "fascism" included social democrats at some point, and their propaganda included bits like "fighting fascism means fighting the SPD just as much as it means fighting Hitler and the parties of Brüning".

I don't know why anti-authoritarian lefties today are so eager to embrace this legacy, or at least its symbolism.