Then charge them with racketeering.

If that doesn't work make the part you don't like illegal. Enshrine something like the "right to be forgotten" stuff into law and make them take down threads if the people they refer to don't want them up.

I know it's hard to word something like a "right to be forgotten" without making it to broad and a tool for abuse of chilling speech but it seems worth the effort if the consequences are this dire.