He's responding to SunsFun, who was calling anyone who looked down on that behavior a loser. And I agree with him.
I mean, realistically speaking, they're both right. If the woman is up front with the man and says "hey, listen, we're all adults here. I slept around when I was young and now I'm looking for security or I've changed and I'm not a party girl anymore," and the guy doesn't mind, that's fine because he can make his decision. But everyone here -- even SunsFun, probably -- knows that's not how it goes down. What happens is that the guy just thinks he was lucky and met some woman who is attractive, but getting older, and that's all. There's nothing "odd" to him because he's always heard that women aren't gold diggers and all of the other "negative stereotypes" about women, so he presumes that she likes him for him. It's rather despicable behavior, isn't it?
By the way, every time I have this discussion, either in real life or on the Internet, what invariably follows is that the person in SunsFun's position then claims that everyone is indeed open. I've had at least six people tell me that "nobody" lies about the number of sexual partners they've had, that they tell all of their sexual partners about their entire past, and that "nobody" cares about it. None of which I buy because "everyone" I know does care about the past, both men and women.