This is harassment directed towards one specific user.
If you find direct offense to their posts, you should let the instance admins manage that through reports. If there is many instances, do that many reports.
But this is basically fascist harassment. A witch hunt.
What, no one can dissent from your ideology? Is it that weak that it cannot and will not handle criticism?
The reverse applies as well. If you want, open your own instance echo chamber and talk to yourself.