Maybe you could rope off a little corner of the forum as a petting zoo for the irredeemably irrational. Much in the way the 'free for all' forum acted when Syamsu or others had their posting priveleges restricted.
This seems to echo a disussion which came up in Jar's thread on Synchronicity about the level of scholarship shown in debates with wildly different extremes such as mammuthus's large lists of primary sources compared to those on both sides who prefer to use partisan FAQs to rebutt each other and those who simply think that their word should be proof enough of whatever claims they may make.
The forum's rules cover many of these infractions. So in some ways this is merely another question of whether it is healthier for the board to sustain a population of scientifically illiterate disputants in order to maintain diversity, or to be much more draconian in enforcement of the rules and risk losing a number of members.
I don't want to make sweeping generalisations, but I fear that the greater proportion of those lost would be from the already under-represented anti-darwinian faction.
I'm in favour of diversity, after all without Syamsu I wouldn't have, hmm, err, wasted several hours of my life replying to questions by Syamsu? But I do sometimes wish that the fringier elements would still make some effort to acquaint themselves with a more evidence based apprach to debate. Syamsu may well have thoroughly misunderstood almost every paper he ever presented in support of his argument, but at least he bothered to present them.
TTFN,
WK
P.S. I miss Syamsu