You've got to take into account the fact that his parents have probably been listening to what the government has been telling them, which is pretty much that marijuana is the biggest drug danger to our society (even worse than crack and heroin I guess) and anyone who does it is doomed to suffer from physical and psychological problems so severe not even people dying of cancer who need it as medicine should be legally allowed to take the risk. In the eyes of someone who has not experienced it before and has absorbed all the government propaganda, it can seem pretty scary especially when your kid is doing it. But if he can demonstrate that he can continue to live responsibly while smoking pot and can show his parents some real information on its health effects, he should be all right.