> It's usually "you don't know what you are talking about," followed by bashing until the person takes their ball and goes home.
I agree that if it's just that kind of content-free junk, it's pointless.
However, if the beatdown comes with a factual and logical refutation of the idiot's points, or at least a link to a site that has such a refutation, then it performs the inestimable service of educating the lurkers.
For example, let's say we had an anti-vaccinationist come here and start spreading lies about vaccines. We would, rightly, be dismayed at such utter lunacy at work in our forum, and we would (hopefully) post multiple refutations of that dangerous nonsense. Ideally, the lunatic would find that we are not amenable to that kind of idiocy and would leave, sadly uneducated (most likely) but at least doing less damage. The real benefit to such actions may come months later, when someone unsure of the facts about vaccines discovers a dead thread that has all of this wonderful information we used to refute the idiot.
(And, heck, we might even convince the anti-vaxxer. It could happen.)