I suppose that if something terrible were to happen to Hillary, and there were a thread about it on FR, and someone mentioned something that the cops knew ONLY the killer and they would know (and the poster was not one of them), they'd look up that poster fairly quickly.
But it looks bad that they have taken 6 posters. Surely all 6 were not involved. There has to be a 1st amendment defense for some or all of those posters.