[Molten]

I read this through and had no clue how to help with either issue. Admittedly, I would have been in as much of a bind as you with no clue what to do. Then I read Jared's response. It seemed just about perfect. I'd do exactly what he said. Also, I have to disagree with Alan's advice on this one. You've already been accused of wanting rid of the student because he isn't in your "group". If you form a support group against him, you'd be proving their point. I think in that case approaching the problem as an individual is much more appropriate. It is ok to approach the student when others are around(as Jared suggested) but I wouldn't approach it as a group. I would also avoid talking about the mentor behind his back with other students. If you find it necessary, be prepared for some yelling. Nobody likes being talked about behind their back. If the mentor is as verbally abusive as you've said, he will likely respond to such with plenty of yelling. And assume he will know. People have a habit of chatting about things and it will somehow work around to him.

Jason