Conservatives, Republicans, Trump-ists, Holocaust or 9/11 or 1/6 deniers, nazis, white nationalists, anti-vaxxers
Loli
Folks generally trying to ruin the fediverse experience for others
Folks who piss me off
If I even suspect it's slightly illegal in my jurisdiction
If I am accidentally federating with any instances pushing this crap, please let me know and I'll block them
(Please note that your inclusion in the above list is based on my subjective opinion and there is no appeal process. Not sure why you'd care about losing access to a single person instance but whatever.)