Filthy mouthed teenager!?

How do I get my 15 year old son to moderate his language. His swearing and name-calling is completely unacceptable. I should not have to be called a 'fat f..ker' and a 'c..t' in my own house, especially when he knows his swearing is hurtful and not called for. He calls his younger brother all sorts of names, and has a nasty resentful and bitter attitude to match, although nothing has caused this (I know this because the other kids are all still nice loving kids). I have asked him to stop repeatedly but am at my wits end. I feel threatened by him and his standover tactics.