Depending on the situation and TM, they will sometimes provide the shirt. Technically, it's a good guest service practice to let the guest enjoy their day in full, rather than forcing them to either spend money or take time to go back and change shirts, since it's Universal's policy that is causing the "inconvenience". That's why I'm almost positive that the guest here was being unruly. Given Universal's flexible attitude towards this sort of thing, it's obvious the guest's behavior, not clothing, was the reason for his removal from the park.