@nus
For reference, the FediBlock tag is a special hashtag used as a sort of early warning system for content that server administrations or individuals on less moderated servers may want to preemptively block.
In order to use it, you take some screenshots as you did here, perhaps some links, of the most egregious behavior being done or accepted by server staff, and make a post beginning with the hashtag #FediBlock, followed by the URL of the server or account, then give at least a paragraph of explanation after that. Attach links / screenshots, CW accordingly (Begin with "FediBlock"), and post.
Staff of servers will see this and verify your report, then choose how to respond. Do not expect every server to block, as it is really a matter of how much bullshit people are willing to put up with. I also don't recommend doing it with single accounts unless you know they've been reported and their staff has done nothing, because we often investigate whole servers.
Hope that helps.