just tell him to stop. i had an addiction, im not proud of it by any means. but the easiest way is to go a couple days without porn for a while, then 4 days, 5 days, 6 days, so on and so fourth. it does work. socially i've made a 180 degree turn, i used to be that kid that sat in the corner and didn't talk to anybody, now i'm out and about talking to real people. breaking the addiction was a great feeling.