Rather than joining up with the leftists, they sided with the fascists

They did battle with the fascists in the streets, and once the Nazis were clearly on the verge of seizing power, they allied with their enemies in government to get behind Hindenburg to try to stop it from happening.

The "rather then joining up with the leftists" part of it is accurate. Of course, the converse is also true -- rather than joining up with the SPD, the leftists did battle with the SPD, called the SPD the main enemy, and even as late as the presidental election in 1932, were still running their own candidate, splintering off 13.1% of the vote away from Hindenburg, meaning that Hindenburg squeaked into office on a weakened mandate and Hitler was the de facto man in charge even before Hindenburg's death. And, all the while and after, the KPD kept insisting that it was all the SPD's fault.

It was the last election many of the far left people saw, since they died in the camps before the next election came, years and years later under allied occupation. It is of course impossible to know whether the ones who died in the camps still felt it was the SPD's fault.

If you live in the US, you might get a chance to see how this all operates firsthand, from inside whatever the modern version of the camps is. You can of course argue that it's someone else's fault, and they should have compromised with you, instead of the other way around. Who knows, there's an argument that you'd be right (and that Biden shouldn't have alienated all the anti-genocide people). Of course, if that happens, your argument of course won't mean shit in terms of saving you (or saving any Palestinian population which is suffering ten times worse under Trump's administration than it was under the one you're currently criticizing, although your criticism has perfect validity.)

I have spent as much time as I want to spend trying to talk sense into you.