By votekicking them on official VALVe servers and non-friendly community servers, preferably using these methods, while leaving IPs/links to friendly community servers they most likely will never join due to their interesting nature.

But let's go and give it a shot anyway:
(they need to paste Steam connect links in their browser, not aware of other options, I never do that, or just launch TF2 and paste the IPs)

LazyPurple's Silly Server 1: steam://connect/192.223.26.238:27015 | 192.223.26.238:27015

LazyPurple's Silly Server 2: steam://connect/192.223.26.238:27016 | 192.223.26.238:27016 ||_often empty, go fill it up like cheaters do with disabled VALVe Anti-Cheat community servers_||

LazyPurple's Silly Server 3: steam://connect/192.223.26.238:27022 | 192.223.26.238:27022 ||_often empty, go fill it up like cheaters do with disabled VALVe Anti-Cheat community servers_||

I don't want to seek servers for friendlies when they are the ones who should do it, so DM me or let me know somewhere in the comments if you know any other friendly community servers.

I'm sure there are more, even if not, it doesn't mean friendlies are permitted to establish their bases of griefers on non-friendly servers.