Actually, forcing people to post outside their comfort zone would be anything but "stifling" in fact, in so doing one may find their horizons broadened. Again, it is not a removal system to force people to post in more then one forum... not that I agree with the idea or anything..but it's simply not one sided ~ it's forcing those that are one sided to post on the other side. Now that I can agree with!
Tossing a few of the worst trolls might serve enough notice. I've seen a few banned that had only gotten up to the level of irritating juvenile in my book but I hadn't been in many threads with them.
If the next couple of guys that traded accusations about kiddie porn and Adult/Beastiality in the middle of an unrelated conversation about "when to submit" suddenly found themselves permanently without a login... and the moderator actually stated that was the reason... a whole new era of civility might enter that forum. That isn't censorship... just forum moderation. It'd go a long way toward fixing the problem in there.