Should I be upset at my boyfriend?
So I let him borrow my laptop. And one night, he was really in need but we just couldn't do it that night. So I saw in the history that later that night he went on YouTube and looked up girls shaking their butts, and when I brought that up to him casually he told me that he masturbated to that. And I was a little shocked, but I stayed calm and collective. And just vaguely mentioned stuff like, "well it wasn't my butt", and "fantasizing?" And I didn't really know what to think of it so I let it go. But then I talked to some of my girlfriends and they said they'd be pissed. So I confronted him about it, and he was all "All guys do it" and those girls don't mean anything to me, it just helped me get off. But I feel that he shouldn't really be looking at other girl's butts to get off... We've been together for a year and a couple months. I am VERY lenient with him on many things. So should I be upset or no?
Thank you!