Hi write or wrong.
I would recommend to be the “voice of reason” for him. At his age, he is very influenced by his peers and this trend of wanting to be cool by going after shtussim.
He may just be testing the boundaries and also note that your words may have more of an impact on him than you realize.
Your support and encouragement for him to do the right thing will help him “go off” a little less, than more, until he matures and is understands why he should be grateful.
Listen, many of us who made it here from there know the appealing garbage is garbage, so…… I hate the idea that some people already “on the derech” have to learn that the hard way. But the hard way is usually a lesson well learned.
Hatzlacha Rabbah!!!