Not sure why he does this?

I've been seeing a guy for about 7 months. We have a sexual relationship and spend most weekends together. Anyway, he does this really annoying thing whereby he tells me about incidents in work where women have come up to him talking making advances, he tells me he feels uncomofrtable about it, but yet humours the conversation by answering. He says they ask him personal questions that arenindirectly asking him out. He doesn't tell them he is seeing someone.
He also makes comments when watching tv things like 'their not nice girls anyway' and comments on the appearance of them and then Google searches them and discusses it for ages.
I like spending time with him, and without sounding like I'm insecure- I don't understand why a guy would blatantly talk this way infront of his love interest?
Any insight into why anyone would think speaking about exs, other women and commenting on women's appearances at any opportunity is attractive, please let me know
I've asked him many times about it an told him I don't think it's appropriate to be amusing work flirt or not being honest about seeing someone.
Do guys do this to purposefully piss a women off or give a hint?
Not sure why he does this?
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