What's the problem, it's just porn. Come on like you never watch skin flick before. Every brothers mother seen a porn before. You ladies to come down and get off that high horse you're riding named bullshit.
He wants to look at some new merchandise. Maybe hes just a little bit bored with your current sex life. Try talking to him about it. Ask him straight up why he feels the need to watch it and better yet why he feels the need to sneak around and watch it. He obviously feels like hes doing something wrong if hes sneaking around.