Why do people love to criticize everything?

If you look at web articles, people are so vicious when they make comments. It amazes me, considering how so many people will die today b/c they didn't get enough to eat, yet people are angry at yahoo for printing an article on how vikings died. Who cares if it's an old article? It's interesting, and most of us got enough to eat today. I don't understand the world. How can we ever get past our need to put everything and everyone down and just be grateful for what we have??