Right now, most leftist groups are so small that even if they all worked together it wouldn’t be militarily significant. So even if we threw out all our values and worked together with genocidal assholes, we would still lose. You’re asking people to sell out their entire ethical framework for a couple thousand untrustworthy allies. That just doesn’t make sense.

As for liberalism, by your own admission it is failing, so why on god’s green earth should we tie ourselves to that sinking ship as it goes under?

Luckily, there is a way out: You forgot that ideologies are made of people, and that it is those people changing their minds that cause the power balance between ideologies to shift. Liberalism is sinking because it has lost all credibility, and fascism is growing because it helps rich liberals preserve their power as the liberal economy contracts and because it gives the western working class a clear narrative of preserving some privileges in spite of that contraction by more violently extracting wealth from the less privileged.

So what we need to do is to have a clear narrative of how leftism will improve people’s lives, ideally one that reflects reality. If we cooperate with genocidal parties, that muddies the narrative. If we cooperate with the liberals who set the world on fire, that muddies the narrative. It is great for the narrative to support diversity of tactics and diversity of ideology, but then we need to weave that into the narrative by explaining the limits of tolerated diversity and the process through which better tactics and ideologies are cultivated.

If we want to have any chance of winning, we can’t team up with genocide supporters. Nobody could trust our promise of solidarity if we do. We might sometimes benefit from giving them resources or coordinating strikes with them, but they are a different faction.