Stupid people story time

A story: Rob and I were going to Target. I was driving and we were pulling into the parking lot. In front of us, there was a car stopped. Yes, Stopped..... right there in the middle of the entrance to the parking lot. With nowhere else to go and my car's butt almost out in traffic, I watched them as a person got out of the passenger side, and stood up, stuck his head back in the car and talked to the two people inside with the door still open. The guy getting out was obviously their son. We continued to wait and they continued to block the entrance. Cars were backing up on the road now waiting to turn in. I threw my hands up to show them frustration and to try to get them to GO. The woman driving looked at me but didn't do anything. Finally, the son shuts the door and walks away from their car and past our car. Then he hits the back of our car as he walks by!! This kid hit our car because I threw up my hands at them for blocking the entire entrance way to the shopping complex. If Rob wasn't on the phone with his mother at the time, he would have jumped out of our car right then and there. Once we got moving, we parked and so did they. We looked at them as we walked into the store and entered at the exact same time. We continued to glance back at them. They started to laugh and joke and said that they were going to call the security guards. Rob and I had a real hard time coming down from that one. We were soooooo close to saying something to them. Something bad could have happened. Surprisingly, we left the store at the exact same time as them too but they didn't see us. Once again, I could have been the car right behind them but I decided to go another way.
How can people have such a disregard for other people?