You've had some bad luck, but sometimes, I have tried to engage in a discussion, but if someone insists on spouting pseudoscience, for example, I will take a snack away for each rambling, illogical, unscientific post -- if only to warn the new people on the board of the general content of that person's contributions. I've seen people with an innocuous post, a bunch of negative snacks, so I read their older posts and ... sure enough that person was stubborn, or rude, or pushy and demanding. And then I knew, just to ignore their new posting.
I've lost dozens of mole snacks when I given some of my best responses -- this thread here:
http://www.chemicalforums.com/index.php?topic=24568.0 caused me to 19 or so, simply because I didn't give away as many answers as these kids wanted. Or maybe that wasn't it -- maybe, trying to help the people learn for themselves, I was too obtuse, and made the regulars become annoyed. It all balances out, in the end.