I cannot see any reason why they wouldn't honour your simple request to repack your bag, return your documents and allow you to try again later.
I think this is a classic case of someone making a decision and refusing to back down because they feel their authority is being threatened.
Worth a quick note to BA to complain about the staff conduct if you felt particularly put about by it, particularly given you couldn't check your bag for safety reasons. But I wouldn't expect compensation and personally I'd chalk it to experience
