All men are going to look at some type of pornography. It doesn't matter if it's in front of you or they hide it. Since it's not affecting your relationship (him choosing it over you) I wouldn't make a big deal about it. You knew about it before and were willing to start dating him again. Maybe he is embarrassed because he talked about it being a problem before and he doesn't want to start fresh with that being a topic...just like you don't. I would probably casually ask him how his therapy is going or how it turned out and that will open up the topic of conversation. Maybe he has had his computer for a while and looked at that site when he was single that is why the porn site title still populated? I would not mention that you found that on his computer, he will think you don't trust him. Or you said you wouldn't mind incorporating it into your relationship... maybe you can see if he will go to a "toy store" with you and you can mention it when you guys are in the video section.
For me I personally know in my relationship my husband looks at magazines. I know it is natural and all men do it, but I can't help but get my feelings hurt like I am not good enough. So, I told him do whatever, but I don't want to see any of it or know about it. It just makes me feel bad about myself, and makes me act like a crazy woman if I find it...lol (I am also 9 months pregnant... I think my normal self wouldn't mind too much). =)
I don't mean to keep saying this, but several months ago my wife gave me an ultimatum..porn or me...I chose her and haven't looked back. One can get over a porn addiction. I've since become rabidly anti porn...and because of my wife's physical condition (chronic pain) we have not had sex in at least 2 years.
It's a strong craving that most men have, and for you, I would advise to not personalize it as some sort of rejection; especially if it is, as you say, an "addiction." So, how do you "... talk to him?" Discussing it in a mature, non-judgmental, non-threatening manner without causing shame and/or embarrassment would be the best way to get your point across about such a sensitive issue.