So I'm not necessarily taking sides, as this is mostly a one-sided piece, but just answering your question of what people might find dirty about this account: the allegedly transactional nature of being a Flayboy Bunny, including the pressure to be part of Hefner's group sex:
> Which is where she first encountered the seven-at-a-time harem that Hefner, who was then 74, maintained. After a year of being a regular at the mansion, and with both of her roommates moving out, Madison was desperate to stay in Los Angeles, and decided she'd try to be one of the girlfriends. (A spot had opened up.) After all, she had been assured that none of them actually had sex with Hefner, and it seemed like a nice — and free — place to live.
> The decision immediately cut her off from friends outside the mansion. Madison said they would say, "'Ew, gross, you hooked up with an old dude?' I thought I was an adult and thought I was making my free choice. And I was. But I wasn't sophisticated or really prepared. And kind of got in over my head. ... I could understand how people thought it was strange. But I guess I wasn't comfortable enough to explain why I thought it would be fun or why I thought it would be a good idea."
> ...As Madison learned her first night out with Hefner and the girlfriends, sex was a requirement of living there. Wednesdays and Fridays were "Club Nights," and Hefner and his ladies would go out in Hollywood, getting VIP treatment at various clubs. (Hefner's fame as a septuagenarian sexpot novelty was then at its peak.) Hefner offered Madison a Quaalude, telling her, she writes in Down the Rabbit Hole, that "in the '70s they used to call these pills 'thigh openers.'" She turned him down, but did get drunk, and by the time they all went back to the mansion, she was told that it was time to go to Hefner's bedroom.
It's worth pointing out that these excerpts alone (which come from a book, which I haven't read in its entirety) don't necessarily allege illegal behavior -- the sex was consensual, as was the taking of the quaaludes. But even for people who enjoy pornography and sexual liberation, the implication that sex was coerced as a matter of employment might feel "dirty".