Before I go any further, Emil, I have to say first that it's more of an easy joke than a serious comparison, and also that I'm not about to get sucked into another Dogzfest just quite yet.
For the sake of playing devil's advocate, though, I'll say this about your three points:
1. Nonsense confined to a handful of threads is less obtrusive than nonsense spread across the entire board.
2. If "participation" means showing up in every thread, I'd rather have my idiots non-participatory.
3. Ignoring the fact that none of us can really know either of their minds (meaning that I disagree with your perceptions and believe that Dogz has a lot of malignant tendencies), the results are more relevant than the intentions. If infidel is a loony with a sniper rifle, Dogz is an infant with an Abrahms tank.
Literature is [the art] best suited to challenging absolutes of all kinds. Because it is in its origin the schismatic Other of the sacred (and authorless) text, so it is also the art most likely to fill our god-shaped holes