After reading some more posts and seeing that vernbal bullying was a major cause for your son’s predicament- I can TOTALLY relate to him. 10 years ago when I was in elementary school, my classmates called me a bum, told me I was going off the derech, took my black hat and hid it, claiming that I wasn’t frum, so I didn’t need it. I would walk into a room and kids would yell out “oh the bum is here” The only crime I was guilty of? wearing bobby pins so I could better keep ON my yarmulka. I did have a tv in my house, but I didn’t talk about that so much. Kids can be vicious. The problem is that they get this stuff from the older siblings and adults around them. A kid isnt born saying that bobby pins mean youre not frum. They hear their parents say it and it becomes engrained in them. It’s really a shame.
I never went completely off, but I had my period in high school when I wanted to distance myself as much as possible from the people who had bothered me for so many prior years. I hung out with girls, went to movies, etc…( I never smoked or drank because I just felt that even from a non-religious standpoint, its damaging, which obviously, it is). Eventually I came back a little more to the right, though not entirely. Sometimes the best antidote is simply time. It is absolutely not true that your son may never come back. I know guys who were very modern orthodox who became very right wing. but nothing will happen overnight, and there probably isn’t much you can do either. I know there wasn’t much my parents did for me. Sometimes, simply the fact that youre a parent will cause the son to disregard what you say. His friend could probably say the exact same thing that he previously ignored from you, and he would listen. Hard as it may be, you really may have to just ride it out, obviously while still being loving and supportive.