I haven't read it. I'm stuck in the first 25% of "Sex at Dawn" and I find I'm hating it (like I hate most evolutionary psych), so I probably won't end up reading this one either. (*)
However, yes, slut-shaming exists, and it sucks.
Showing your mono GF that the way she is is wrong is a BAD way to go. I'm mono, I went through this with my partner. Suffice to say I reacted badly to being "converted."
Yes, some of it can be societal (the "I want YOU to be faithful to ME" portion of monogamy can be that way). Some of it isn't. I partner with one person at a time. I just do. I'm not repressing anything. I'm not doing it because I don't know any better. I just do. Telling me that I'm wrong only serves to alienate me. Telling me that I'm only mono because society tells me to be is insulting as well, as though you know me better than I know myself.
Whoops. How'd that soapbox get there?
Anyhoo... slut-shaming is real and awful. There was some news story about a 15-year old girl who got sexually assaulted, is now pregnant, is going through with the pregnancy, and her jackass neighbors are spray-painting "slut" and "whore" and various other epithets on her house. Real kind. That's the kind of crap that makes you want to repress anything that makes you look "promiscuous" to others and GETS young girls pregnant because they're too ashamed to get birth control.
Ah. Another soapbox. Whoopsie.
Not barking at you, onoma! The social aspect is tough in general, mono or poly, sometimes. Just watch out for that polyvangelism.
(*) Why do I hate evo-psych? Because it drives me crazy to hear that prior to <pick a point in our evolution>, we were the healthiest/best equipped to/best <blank> ever. Evo-psych tends to romanticize those points in our history while talking down how we've evolved societally or biologically, or whatever. Meanwhile, I tend to think things like higher mathematics, arts, poetry, science, space travel, you name it, is a pretty good price to pay for evolving past our "prime". Which pieces do you pick from our history, and which do you throw away from our present? You can't have both. Yes, let's understand where we came from, but let's not demonize who we are now.
Crap, now that's the third soapbox. I'm getting out before anvils start showing up.