Some communities there are literally calling for the annihilation of Ukraine
https://programming.dev/comment/1999097
edit: Since people are either willfully or otherwose are missing my point, this is a pro-russia, pro-fascist hate group, therefore we shouldn't give them the platform to spread their shit. this is not about me seeing their community or then causing issues accross other communities, it's about de-platforming fascists.
You can filter them out with ublock origin on desktop and Sync for mobile. It's the easiest way to get rid of Hexbear for you outside of migrating to a new instance, and it's a lot easier than trying to get your instance admins to defederate
you should probably read my whole post definitely the edit part, also Lemmy has built in functionality to block communites you don't need ublock.