They were right to stop him from entering the park, but I don't see a reason to celebrate stopping nothing from happening. Carrying a weapon and firing one are two very different things. When they effectively stop something bad from happening, should it happen (hopefully not), that's when they'll earn my respect.
All they did really was enforce company policy in this case. Could have been a selfie stick, for all I care. If it's not allowed, it's not allowed. Really though, they didn't prevent anything bad from happening, just created the illusion they did.
EDIT: That said, security is a serious matter and I'm glad they show zero tolerance.