It's FOSS, so fork it and host it yourself or find someone else you like who has/can do so. I don't personally think it's too surprising that this free (as in freedom) platform was created by and initially attracted leftists and anarchists, and even if it is, I think it matters far, far less than everyone seems to think it does.

Serious question: Since it's a federated system that is open-source, what do their political views have to do with supporting the platform? Even if they decide to become Neo-Nazis and change it, the rest of use can continue to use the work they've made thus far and keep it like it is or improve on it. Our use of it doesn't support their political aspirations either aside from their beliefs in federated social media.