Why are some people so mean to others?

Some people don't feel very good about themselves, so they put other people down, to make themselves feel like they are better than the others. When groups of people do it together, it's called religion. They get together in their place of worship, and they're told how the way they've chosen to go is better than everyone else, so they get to feel superior. Since that can lead to guilt, since deep inside we know we aren't really better than them, some religions make it okay by "praying for them". That would be like a mean person saying "How can you live with yourself being so ugly? I hope you'll be able to get plastic surgery some day.", as if the second statement makes them not seem like such a horrible person for saying the first.