If you see something hurtful or nasty on the Fediverse, you have a range of options.
You can mute, block or report an account by clicking "..." underneath their post.
Muting means you won't see their posts but they still see yours.
Blocking means you won't see each other at all.
Reporting means you will tell your instance admin (and optionally their admin too) that the poster has broken instance rules. The admin(s) will then decide what action to take.