Help!!!!! I Think my son is being brainwashed by his girlfriend.?

Send him a note that you love him and will welcome him back with open arms if he ever wants to contact you. Explain that you don't like his choices, but recognize that he has the right to make the choices he is making. Acknowledge that the gf is not treating him right, but that you respect his right to make his own choices. Let him know you love him and are waiting on him to contact you. Good luck.