I can sort of understand why tbf. Just playing the devil's advocate here but the issue is that today it's fine and shitposts are shitposts but Poe's law will come into action at some point.
That's not the actual reason. Hexbear was openly advocating for their "army" to brigade other instances once it was federating. It just so happens that the basis of that brigading was going to be political.
Lemmy.world pre-emptivly decided it wasn't worth the hassle of having to deal with that.
what's the line between brigading and just getting into political arguments though? cause hexbear is plenty good at the latter, they used to fight among themselves a lot, but doesn't really have a huge history of the former, they mostly keep to themselves since the reddit ban. Most I've seen is a handful of accounts posting in the defed announcement thread here, which like, fair enough, it was clearly a politically motivated decision. It's hard to believe they'd be any worse than lemmygrad for example, if anything they fit the culture of the wider lemmyverse a lot better (not to say lemmygrad should be defed'ed either by a general purpose instance such as this, but there is more culture shock there than hexbear)
it's worth noting that the statement about the war in ukraine is written by the people who run the news megathread, not the whole site, and the degree to which people agree with them seems to vary widely. It's been the subject of a fair amount of arguing on the site in the past.
But the seeming majority opinion of say, lemmy.world, of outright supporting NATO unconditionally is probably further than even the most skeptical hexbear user would go, give or take a few outliers. The majority lie somewhere inbetween, with most people disliking both russia and NATO, and thinking that NATO influence is serving to prolong the war, not shorten it.
So from the perspective of a US liberal they are outliers yes, but they aren't a monolith who all love russia either, and they are very accustomed to being shat on from both sides of the US and EU political spectrum as russian bots, CCP shills, etc. because of their communist views.
Oh I'm not saying the overall opinions there are ironic and will stay that way, they are very much communists (and a notable minority of anarchists), and that isn't likely to change, just that there's also a lot of shitposting, and the general jokey tone seems to be what convinced admins not to take the "hey guys you have to follow the rules of federated instances when you post there" seriously