I'm thinking back to the seventies and the riots outside perfectly legal National Front meetings. The result, apart from a load of trouble for the police, was extra publicity for those inside and good publicity at that. I was a student at the time and we had similar problems with controversial speakers at the students' union and the many attempts to disrupt them. I came up with what I thought was a brilliant idea - though it seems that nobody else agreed because I don't think it ever happened.
You quietly pack the hall with as many of your own supporters as possible. Get in early and fill all the seats. So far so good. You don't heckle and you don't throw flour bombs. You just sit and listen, waiting for the speaker to start some objectionable rant. It won't take long. At this point you quietly get up a few at a time and walk out in what looks like disgust. The geezer on the platform will be left talking to an almost empty hall. More effective than any flour bomb don't you think!
Where is all this leading? I put it to you that if you find some offensive post on this forum you should not waste your time replying. Apart from anything else this means it keeps coming back to the top. Ignore it and it will slip silently into obscurity where it belongs.