ok, since I'm seemingly not really doing anything useful today, I'll use my own words to state something from that video. (so i'm not the smart person behind this; that's ian danskin/innuendo studios, self-identified cis guy)
when there's a "no politics" policy, what does that really mean?
well, "politics" actually means controversy here. "don't talk politics" really means "don't cause political conflict". ian points out how "nazis are bad" is an uncontroversial opinion and therefore also non-political. but therefore, "nazis are good" is also non-political, since nobody will defend it! it's obviously a joke. it doesn't cause conflict within the group because everyone disagrees.
"trans lives matter" DOES on the other hand cause controversy within the group, so it is considered political and yields a warning. (yes, on fosstodon)
what this means is that being a nazi is considered non-political and allowed, while being trans is on the other hand considered political, so you better not talk about it—and if you do, then you are ruining the community with your political agenda.
now, it's worth pointing out that fosstodon doesn't actually have a literal "no politics" rule. instead, it has a "don't cause political conflicts" rule—and that's the exact thing that "no politics" usually means. look, they made it super obvious that the above is what is going on:
3) Do not be intentionally antagonistic. A post or reply designed to provoke a confrontation is not acceptable.
and that's part of the alt-right playbook.