1. People talking about their exes IS a turnoff, true.
2. An attractive woman in her mid 20s who has been with a double digit number of men is a normal human being. Not "slutty", the "town bicycle", etc. Where the hell do you think these women learned these sexual skills? Sleeping with 20 men over a 10 year period is not exactly a blistering pace. It means, typically, that they had a handful of longer term relationships, several shorter term ones lasting a few months each, and a few one night stands here and there.
3. The main character is on pace to fuck a dozen or more women, including every woman in his family/household, in a matter of several weeks to a few months. He's a turboslut, by the above standards.
I can understand why any extensive discussion of a partner's sexual history may be a turnoff, but let's at least adhere to a consistent standard that applies to both genders, yes? I guess we can stick with the double standard for another few thousand years, but I'd prefer not to.