You can't tell him. It doesn't work.At 15, he should be able to figure things out on his own. Any words from you, painting the father in negative colors would only earn you the reputation for being a villain and a drama queen. If the father is exactly as you describe him, your son will come to realize it soon enough. Based on his critical skills he would measure words against actions. He will ask to be removed from said environment himself unless it works for him (at 15, most kids are very independent and territorial, yet completely receptive to bribery).Alternative version: if you have the money - go ahead and sue the crap out of him. If not, look for legal aid services if they exist where you are. Get online and research that part of the law very well. Prepare yourself and think of what you can gain now. Visitation is a parental right that cannot be lost. File for it. It will return results. Once communication is re- established, you can be his mother, and have any conversations that do not involve the father and what he is. Save your nerves and sanity, you are going to have to keep them intact even if the rest of you isn't.Good luck