OK. So we have two scenarios:
1. You're camping and you notice that someone is setting up camp in a spot that you know is reserved starting tomorrow. You go over to let them know and you are labeled RUDE;
2. You're camping and you notice that someone is setting up camp and parking their rig. You go over to let them know that they are doing it wrong and you will correct that and are labeled JUST BEING A NICE GUY.
Really? I'm sorry, the guy in #1 was no ruder than the guy in #2. The guy in #2 was no less rude than the guy in #1. They both made someone else's business their own without invitation; they both attempted to stop a potential problem from taking place.