namecheap dropped entire population of russia and belorussia as customers

https://www.theverge.com/2022/3/1/22956581/russia-ukraine-na...

sure, an extraordinary example, but what stops anyone from wording their ToS ever so slightly vague, that any domain is held by a shoestring

They weren't holding the domains hostage, though, right? You can find any other registrar willing to have you and transfer your domain from Namecheap to them (and I think Namecheap would get in trouble with ICANN if this weren't the case). So customers are mostly just inconvenienced a little.

So long as you provide ample time to transition and sound reasoning, firing customers you can't effectively service is the best thing to do.