What would you do if you caught your SO masturbating to pics of his female friend?

My bf and I lived together when this went down. I was very upset and felt disrespected and betrayed in a way, but I moved past it on the condition he block this girl on social media. Come to find out he simply unblocked her a little while later without saying anything. I’m mad, but he says I completely overreacted, that my request he block her was unreasonable, and I should “see someone” about how sensitive/jealous I am over this. I have trouble believing I’m the only girl who would react this way, but now I’m curious if I really am in the minority. Making matters worse was that when I caught him, we were often fighting about sex - I wanted him to initiate more, but he just had “a lower sex drive.” So to find out he was lusting after that other girl in this way was especially hurtful. Anyway, what would you do? Am I going too far in asking that she be blocked?