Porn's Dirty, Dangerous Secret
There are a finite number of ways that human bodies can fit together. So pornmakers resort to sexualizing degradation to stay "cutting edge".
Gonzo producers test the limits with new practices that eroticize men's domination of women. Less intense forms of those sexual practices migrate into the tamer feature pornography, and from there in muted form into mainstream pop culture. Pornography gets more openly misogynist, and pop culture becomes more pornographic -- many Hollywood movies and cable TV shows today look much like soft-core pornography of a few decades ago, and the common objectification of women in advertising has become more overtly sexualized.
Where will all this lead? How far will pornographers go to ensure their profits, especially as the proliferation of free pornography on the internet adds a new competition? How much eroticized misogyny will the culture be willing to tolerate?