Adviser-Poaching and the Politics of Graduate School
The damage has already been done in this situation, and your boyfriend should move on with his future.

Basically, at this point, I don't see any way in which the relationship with his current advisor can be mended. The name calling and guit tripping makes for an impossible working environment. Even if he were to stay, he would have to deal with the cloud of the previous attempt to leave hanging over his head. Therefore, it is in his best interests to find a new advising situation as quickly as possible.