I work at a university. We would take this, especially the personal comments, seriously. It’s not an RA issue. RA issues are a difference in preferences for thermostat settings and similar disagreements. It sounds like the roommate is creating a hostile living environment.
Your son should be documenting what the roommate is doing/saying (dates, times, witnesses). I’d recommend seeing a counselor on campus for suggestions on dealing with the roommate, then go to the Dean of Residential Life with his documentation and tell them he wants a room change. Start creating a paper trail.
In the meantime, he should live his life. Invite people over, go to events without explaining his schedule to the roommate, and quit giving in on things he doesn’t want just to avoid conflict. The roommate can only run his life if continues to let him.