The "S" word

For a while now the word s**t has bothered me, but not in the way it bothers most people. I'm sure that most of us can agree that s**t is a "bad word", but why? As far as I know s**t is another word for poop. From an early age we a discouraged to use the word s**t and in many cases we are not supposed to say poop either, so we have to make up names like doo doo. So if doo doo is another word for poop, isn't it the same as s**t? But one is encouraged and the other is highly discouraged. Weird.