happyone2 is right - men do like looking at naked women because we are biologically programmed that way. What is not programed is his insensitivity to the fact that you have advised him that this upsets you, and he is still doing it.
Don't approach this from a 'them rather than me' angle - every man looks at naked women, no matter how gorgeous his partner is.
You should talk in terms of the fact that he is ignoring your insecurity, which is rude and insensitive of him, and he needs to stop. If he makes light of it, tell him you don't, and it is causing an issue.
You could always try openly leering at every fit guy you see when you are with him - no jokingly, be discreet,, but make sure he sees it happening, and if he asks you, tell him if he likes it?
If your man wants to be 'one of the guys', he can pretend to look at the pics, then delete them.
You need to sort this out, it is a relationship issue, and it's not going to go away.
Good luck.