That is extremely unprofessional. My friend went through the same thing. A student asked a professor if he knew my friend and the prof replied "yeah....I don't like him". Just flat out like that.

I don't really have a solution except to try and be the bigger person. If this adviser acts like this enough, he wont last long.....unless he's tenured. Then they're invincible. Have you tried to express your concern to someone who might be able to talk to him about it? He needs to realize that, no matter your personal opinions, you don't talk about students like that to other students.