My lhasa apso viciously chases his tail, he hates it! what can i do?

I know loads of dogs chase there tail, and it can be quite humorous, but my dog is totally different. I've never seen a dog do it like this before, he literally attempts too attack his tail, too the extent were he actually pulls hair out of it. He hates people touching his tail, or going near his back end, he has bin known too bite if people who go back there, he growls first too warn them off, so they normally get the message too back off.. ( but i always aware people not too go back there & i keep him away from children so no one is in danger) I am very worried though, because even if uu walk past him, and happen too accidentally brush his tail, he goes off on one! it can be very scarey for people who witness it, as he makes a snarling growling noise as if he's going too attack, but then he just goes for his tail (continuing the noise). I have tried everything i can think of, i have too restrain him when he goes for his tail, as i can tell it upsets him, its as though he isn't aware its part of him, and thinks its an other animal. I was thinking that maybe i should ask the groomers too cut all the hair off his tail, in hope that would maybe stop it! But that will have too be the last resort, as my dog groomers will not be too happy in doing this. Im sure yous all know lhasa apso's have a curled tail with quite a bit of hair on it. I am at the end of my tether, i really do no know what too do, and i don't want my dog too be in distress..any suggestions?