Regardless of all of that, you would be surprised how difficult it is for airlines to actually ban people from travelling. There is a legal process that needs to be followed that, in Europe at least, seem to favour the passenger. As an airline we can offload them, we can have them arrested but to ban them is an entirely different matter.
Can you just see the media hype "BA bans nervous passenger". As much as I'm sure they'd like to, they just can impose these sort of sanctions against someone who really can't help it.