If he is able to keep his board clear of this type of infiltration, it will be because it is so slow and insignificant that it can be managed.
I don't think he'll have any better luck keeping the whackjobs out than anyone else. All we can do is to judge the posters by the comments they make. If it looks whack and sounds whack, it probably is whack. Doesn't do any good to contribute to whack, nor to debate with whack.