I really think that either you or DH should talk to him about it. The problem with porn is that it's completely unrealistic and he needs to know that; most women don't look like porn actors and the sex acts themselves that are portrayed in porn aren't realistic either. Porn makes the woman into a sex object with no desires or personality or feelings of her own, her soul purpose is the sexual gratification of the man. Porn is degrading to women and because of that, has been directly linked to negative attitudes about women, and also to rape, in many studies. Several studies have shown that after looking at pornography, the men surveyed felt increased hatred towards women, and expressed more misogynistic attitudes. You can't really stop him from looking at porn, but you can at least explaint to him (you or DH) why it's unrealistic and NOT a good thing to model sex upon. Also, some porn is worse than others; it's far less damaging for a person to read a playboy than to watch a hardcore porn DVD.