I'd tell him to set himself up for success. His activity was innocent this time but by creating situations where he has the opportunity to do so not-so-innocent

I'd tell him to set himself up for success. His activity was innocent this time but by creating situations where he has the opportunity to do so not-so-innocent things, he'll give in to the temptation someday. It's like working at McDonalds or KFC: there is a big chance that you'll gain 2-3 lbs ever month you work there because sooner or later, you'll eat there. He shouldn't put himself into such situations where he can screw up. Bad decisions snow-ball.