The faith y’all have in the US justice system is misplaced. The cops absolutely will not show up even for blatant online threats.
Oh, but they do!
Texas Man Sentenced on Cyberstalking, Making Interstate Threats | USAO-WDVA | Department of Justice
Man Charged in Miami Federal Court with Making Online Threats to Injure and Kill Young Woman | USAO-SDFL | Department of Justice
Florida Man Pleads Guilty to Cyberstalking | USAO-WDVA | Department of Justice
Officials Announce the Arrest of Thomas G. Bares for Threatening Communications — FBI
And the list goes on and on, including those for instigating hate crimes on the Internet. Threatening communications, whether by telephone, mail or the Internet is not taken lightly. I do have a lot of these links as I receive email updates constantly from the FBI and the Justice Department. (I hate those with up 60 in one email. ) Authorities would rather “nip it in the bud” before someone gets physically injured or worse.
Edit: This last case I’ll post will show what the consequences can be.
NEWARK, N.J. – A Bergen County, New Jersey, man today admitted using Facebook and other online web forums to cyberstalk victims, U.S. Attorney Craig Carpenito announced.
Diamante admitted that from January 2016 through August 2019 he engaged in continued online harassment of known and unknown adult victims, including Victims 1-23, …
The charge to which Diamante pleaded guilty carries a maximum sentence of five years in prison and a $250,000 fine. Sentencing is scheduled for Dec. 16, 2020.
Forum X is well justified in restricting members who use forum content inappropriately elsewhere.
Back when I was an Owner/Mod for a very active Community on G+, it was our policy not to condone trolling/mocking behavior on ANY forum, including inciting others to do so (“calling out”). Responsible Community owners were happy to reciprocate. For the irresponsible owners (there were organized trolling groups) we were often able to get those groups shut down by reporting them for violating Term of Service. This could be a game of Whack-a-Mole as new groups formed - Google has quietly giving up on G+ so support was not as strong as it should have been.
If the forum Y owner won’t support you, contact their provider and report these activities. Provide screenshots, URLs, dates and time, and accounts to back up your complaint. Be sure to quote specific wording from that providers Terms of Service.
Here’s an interesting but old topic from CodingHorror (2014) that hits on this problem. You can disregard the description about people signing up through Tor, but the main discussion is about hate speech and “this is our house and our rules.” You don’t have to host their hate speech.