Banning all photography seems extremely overbroad. If Comic-Con had an explicit policy for what constitutes harassment, and a method for attempting to enforce it, it could reduce a lot of the negative behavior. It would also educate attendees who wrongly think they are allowed to photograph anyone. I'm gonna guess that most people who dress up want to have pictures taken, but they want control when, where, and by whom, which is all reasonable. So post signs indicating that you must ask permission to take photos of other people, and create a means to punish violators. The idea of an area you can go to where photography is permitted in general is also a good idea.
As it stands, the policy appears woefully inadequate.