Maybe an identifying marker should be put up on a thread when the blood starts to look like flowing, so that people who don't enjoy that sort of thing can boycott it, and those who do can crowd in like boys in a school playground crying "Fight! Fight!"

After all, it can happen in the most innocuous sounding thread (music related or BS) - and conversely, threads with headings that sound highly provocative can turn out to contain good-mannered discussions.