If the main notice/access to the crank forums were not automatic there would be little problem either as there would be no one to take notice but the cranks.
For what it's worth, it isn't so much that we mods don't care what is being posted (if only you could see some of the backroom posting going on, as we are, in fact, trying to drag SciForums back to a site where the Scientific Process is a standard) but rather, trying to balance maintaining a semblance of real-science against not simply removing 2/3 of the forum population that never posts anything truly scientific (numbers obviously exaggerated)
There's a vast difference between removing those "who don't post anything truly scientific" and those who post out and out un- (or especially) anti-scientific crap. The more the latter type are tolerated the longer the problem will go on.
Yes, it seems that it would be easy enough just to eliminate the nutjobs. Why have a sub-forum called "The Fringe"?
I expect that by the time an issue is brought to the attention of Staff for moderation, the discussion has often evolved to include more reasonable side discussion and/or comment... Which would make the decission about how to handle moderation difficult. The name calling by even those attempting to present a mainstream view, is likely also a complicating issue.