I catch my boyfriend lying about watching porn, however, we watch it together! What should I Do?

I caught him lying about it, cause he was using my computer. I told him that I don’t mind, just don’t lie about it. So, he started using a different laptop. I looked on it one day, I had a hunch that he was lying. And I was right, as soon as he thought he could get away with it, he kept doing it. We finally started watching porn together while we are intimate. I actually like it, told him there is no reason to lie. It’s no big deal. Most recently, I caught him looking at porn in the livingroom while I’m in the other room. He immediately closed out the window. That made me look again and I go to find that he is quite into bukkake. It baffles me how I could be so understanding and he continues to lie. We have a great sex life, I think and don’t understand why he would do that when I am in the other room. I could see if we were apart but I am right there. When I brought it up and asked why he continued to lie he gets mad and tries to flip it on me. He doesn’t seem to understand or doesn’t even acknowledge that it hurts me when he hides things or lies, period, especially when I create an environment where we can talk about and do just about anything together!