What makes reasonably intelligent " adults" (40s) act this way?

Some people just can't help but poke their nose into other people's business. Sometimes the best way to handle these people is not to antagonize the situation, so just a big smile and something like "Hi, I do hope I'm not in your way, I'll only be a minute." So that you're taking the wind out of their sales. I've met one or two people like this in my time and when I was younger I would have given out to them, thus making everything worse. I've learned that it really is best to keep calm and polite in these situations. Funnily enough there was a guy recently at the check out in the supermarket and he was clearly annoyed that I had let someone in front of me, who had only one item and I had a trolly load. He was very loud and sarcastic so I asked him if he would also like to go in front of me, he said I would be there all day if I kept letting people in. So I just continued to chat to him, pretending I thought he was being chatty and nice. He calmed down as I refused to be intimidated by him. Just know there will always be people with whom we come into conflict with outside of the home, they may be angry, crazy, or drunk or drugged or just plain pathetic individuals, you can't change them just change the way you handle it and don't let it get to you.I bet that guy you met at the car park feels a bit foolish now.