Why are some words considered to be Real bad words.
In English, bad words universally either refer to sex or defication (or the parts of the body involved.) This isn't true for every language, I guess - according to my wife Russian swear worlds (
mat) are all sexual.
But the real reason is rather circular - they're considered bad words because they're considered bad words. Language is created by the speakers, so if a community agrees that a word is bad, it becomes bad.