Not at all but is a very strong reason not to collaborate.

Can't work with someone who is radicalized, they tend to take criticism as attacks and will attack back, sometimes preemptively if they get paranoid and start seeing ghosts.

In those cases only use it if you can maintain it and fork it. Because you can't trust that someone with so extreme political views will not remove the software because they don't agree with whatever downstream group using it.

Yes, because you're giving them more power to disseminate their views and later suppress yours if they so choose. In this case it's a bit different, since it's a federated model, so you can just run your own node, but I'd rather not support the work of people with extremist views.

If they're unwilling to work with people who disagree with them politically?

With federated services, then at very least the people making the technical decisions around the protocols should try to be politically neutral.

The cost of the actual implementation being under the control of political idealogues is less, since forking doesn't impact the API - but it's still not desireable.

Well it depends, right. If their views are just their views then no, not really. But if they outright tell people they want nothing to do with them unless they think exactly alike, yeah, why would you want to contribute to that? When I say they're Marxists, I mean they're not shy in saying what they think of you if you're not one. These are not weekend "what Mao did was wrong" socialists man, they don't want to hang around you either.

I never said you shouldn't? I was only backing up the other commentor's claim since many people might think he's being hyperbolic rather than them overtly spelling it out on their site.

Would you want to be associated with people who openly and unironically praised Hitler?

Pretend for a moment it's a Nazi-espousing group. That's how some are seeing this group even though they swing the opposite direction into Marxism.