The downside is that it would probably just end up increasing fringe and dangerous behaviors

This reminds me of a different type of “banning” I heard about some 20 years ago. There was a physicist who had a separate mailing list for laymen who would mail him to discuss their pet theory. Since he didn’t want to be bothered with them he added them to the mailing list, telling them that they would have the chance to discuss this with other experts in the field …