Since you didn't give the sever name, I'll put this in the general discussion for now. No name cannot go into the review or rant section. This isn't an issue with the listing so not in the report section neither.
The fast and easy solution would be to move and get your friends to move with you to a better server and then start over. If you are not happy with the situation, they should be on the same boat too. Are your friends fine with the harassment? Do they get the same treatment as you?
You didn't take a guess on why the GMs allow the harassment to continue except that the GMs find them annoying to deal with so they just give up and let the server suffer? Is there other possibilities? Such as they want the population even though they are bad apples? Are they donator? Are they GM friends? Are they all in one guild so if they leave the server will lose a high proportion of population?
If the case is as you described, then the GMs fail their job and there is no point to stay in the server there is no future. Basically the harassers control the server, you will not see any new player stay on the server for long. Anyone other than the harassers will eventually leave.
Depend on how many are on your side, the last resort you could do is tell the GMs you and your friends are leaving if the harassers don't stop. See if the GM choose you guys or the harassers. That will give you a definite answer as to stay or leave. But be warned you and your friends could be @banned by saying that. It isn't unheard of from abusive GMs.