I'm confused..There is a born Muslim, once he grow up, he becomes an atheist or whatever. Then what he is supposed to do? He stops praying, stops fasting in Ramadan. that's all right? In such a case, somebody is gonna force you to go for prayer or make you fast in Ramadan?

Belief is in your mind, nobody knows about it. You may pray not pray, its up to you. Keep it with you, who cares??

But yes, propagating your belief is another thing...