I do believe and agree that there are a bunch of people who are lost causes. But I don't think that makes truth unimportant. There's a bunch of people still who do care about whether people are lying, who do think less of the left for this and would think better of it if the left, collectively, were more honest. I'm not American so I don't know how many Trump voters this applies to (people would have you believe "none", of course) but there are also swathes of people who think "both sides are just a bunch of lying bastards." Well, we can try to tell them that, no, both sides are not the same. But also we can not be a bunch of lying bastards.

Fundamentally, I don't think anti-fascism wins by throwing away the principle of truthfulness. Aren't we supposed to be better that?