Great, valid point, but I see it differently.
Lets say you go to the beach, and you put a towel down in the shade. You decided to go swimming, and when you return, I have moved your towel out into the heat. I tell you that "its a public beach, and you left. Just because you set out a spot, doesn't mean it is yours. If you wanna keep the spot, don't leave". What goes through your mind?
Or you go to a movie theater, and you leave your coat on the seat while you use the bathroom. When you come back, I am sitting in your seat, next to your lady () When you ask me to move, I tell you "its not your theater, you can't tell me to move. If you wanted to keep that spot, you should have never left". How would you feel?
Last one. You go to the food court in the mall, and buy some food to eat. You sit down at a table, and you realize you need a drink. You leave your jacket, and maybe even your meal there. When you return, I am sitting in your chair. I tell you "this is not your food court, If you wanted the seat, you should have never left".
With me, its not about property, or public space. Its just courtesy. With digging out a spot, I see that someone has worked hard to get it out. I believe its their spot. Before, I have parked in spots, and left my number on a piece of paper, saying "just needed to borrow it, call me and I'll move". I dug a space out at my parents house when I went to help them out, and I left it open. No laws, no right, just an understanding.
I can see your point, I just think we disagree.