K.C.
I would have him checked for Tourette's Syndrome. The fact that he tells you he "HAS" to get the words out means that maybe he can't really control it. My son has the same issue. He's PDD-NOS (another autism spectrum disorder) and also has tics, both verbal and physical, because of Tourettes. I wish "dammit" were the worst word we hear from him. He's 12 and knows ALL the bad words, unfortunately. Our home sounds something like this: "F&*k!"..."Hey, watch your language!!!" "Sorry..."......................"Sh$t!!"... "LANGUAGE!!!"... "Sorry..." He's able to control it (with lots and lots of effort) in public, but at home, in his comfort zone, we let him get away with it a lot more, we just give him the "WATCH YOUR LANGUAGE!!!!" reminder.