Atheists Why do you care if someone's religious?

You think people are stupid just cuz they have a religion. I am religious and yet I don't go and preach to anyone who is not of my religion. I don't go demonstrating my religion in public. I don't even talk about my religion. So I don't see why you guys have a problem with people and their religion. Its their culture and their way of life. Why can't you guys just butt out of other people's religion if they are not bothering you with it? Or do you guys have a problem with Theists because they believe in an entity greater than them?