Towers do have the right to refuse access to anyone if they feel there is a risk to them or anyone else, as do all theme parks. However they have to do it in a dignified manner and maybe point the guest to rides they can go on, which obviously wasn't the case here.
I was wondering what would happen with Duel due to the fact it only has two walkways, entrance and exit, with an access door halfway up the (narrow) exit ramp leading to the load platform. If they really can't find a way around it they really should inform guests upon collection of the wristband. Common sense I think.