To me it goes bad once you start going after specific people, even nameless people. If you have a viewpoint, that's fine, disagree, have a New York style verbal debate, but then shake hands and move on. And keep it about the viewpoint, not the person you disagree with.

Edit: the /v/fatpeoplehate group was formed before the fattening, the mods kept saying that the subreddit was going to be banned (oddly enough the people on fph knew it was coming probably a month before it happened) so they made the place on voat beforehand. It was around when they went after the images of the imagur people.