Let's see, you don't like porn, and he does. You confront him when you find it, and he denies it. Gee, I wonder why he'd do this...
Were I your boyfriend I could: A) Tell the truth and have you go batshiat on me, get angry, and have to deal with your faux porn drama because you're a prude... Or, B) Play stupid and hope the drama is minimal.
"Well, then," the Cat went on, "you see a dog growls when it's angry, and wags its tail when it's pleased. Now I growl when I'm pleased, and wag my tail when I'm angry. Therefore I'm mad."