I have just ended a two and a half year relationship with a man who did similar things to your boyfriend.
Examples: On one of our first dates he informed me that all of his ex's 'had big tits!'. Don't ask me why I carried on seeing him after that.. I don't have an answer.
When a young woman with a pert bottom walked past us one day he exclaimed "she would be getting it up that!". Again, please don't ask....
We were walking on a beach once, he clocked a young guy who was taking photo's of his GF who was wearing a bikini. I hadn't noticed this, so my ex had to make me aware by saying "did you see that, she was doing all dirty poses, my jaw was on the floor!" I told him that they were just young kids and that he shouldn't be perving at someone so young (he was 49 at the time, this girl was about 17/18).
This was a guy who had a problem with ejaculating due to a surgery that he'd had in his younger years. He didn't have sex with me very much, we had periods where we didn't do it for up to 3 months!
I believe that all of my ex's disrespectful behaviour stemmed from the fact that he had a sexual inadequacy. His crude comments etc were over compensation for him lacking in certain areas. He loved to tell me stories of how much he used to ejaculate in the past, before his operation.. again, insecurity.
I ended my relationship with this man just over a month ago. I'm so much happier now that I don't have to listen to his immature comments and inappropriate behaviour. Ultimately he is the insecure one and I think the same goes for your partner. I think, like one of the PP's said, your partner may have some sort of issue. Maybe he has a low sex drive or some other sexual problem?
I would advise you to dump this man. He will obliterate your self esteem with his comments about other women, you will find yourself forever comparing yourself unfavourably.