We seem to be in different stemit worlds - what topic(s) are you talking about when this happens and how does it happen without you knowing how it starts?
I've read of a crazy downvoter once in the past - I read at the time that if you get your info to the whales they will come over top and down-vote the offender if you can show what happens.
Also - in chat you can actually block someone, I think. Maybe doing that instead of engaging over there might stop the person from hitting you on steemit where it matters the most.
What I am referring to is Steemians (usually people with lots of Steem Power) that use their flagging ability to censor users and posts with opinions or information they don't like (instead of using it as intended: to report spam, plagiarism, hate speech, etc.)
Like I said before, I don't know details about how this last incident (the one that triggered the most recent posts on this behavior) originally started, all I know is that in the end one well-established user (sadly, one of the people who actually produces original, well-researched quality content) got not only their pending rewards but also their reputation wiped out down to zero by a whale who antagonized with the contents they were posting.
That would imply for the rescuer whale to directly pick up a flag war with another whale, which doesn't sound like something many would be willing to do.
Even if they do, the problem is that some people are very persistent. In this case, even though the affected person had a whale on their side helping restore the lost reputation score (if not the rewards), the crazy downvoter kept coming back every day using their full power to downvote everything back to zero. So in the end it just becomes a war of attrition. And that's having a whale on your side! Imagine the situation with most minnows who don't have "powerful friends".
I don't see how blocking someone on chat would help to prevent their enforced censorship on Steemit, since they would still have full access to your content and are free to flag whatever they please.
What general topic are they censoring? I know some of the alt-health stuff or conspiracy issues can get people upset. Is the bad guy checking the tag and going after all steemers on the topic, or just after one person with a vendetta?
I saw a comment (long ago) that mentioned the idea of taking these type of bullying issues to the whales no matter who you are or who you know. I'm not knowedgable on the various whales, but maybe jerrybanfield would be one to take this problem to. He's pretty helpful to little guys.