> The claim is that, empirically, many (or enough) of the women who end up in porn are underage, trafficked, or psychologically coerced (due to poverty, drug addiction, abuse, etc) such that the choice is not really the free choice of willing participant.

The main point of contention becomes what "enough" constitutes. Almost no women in commercial porn is underage as all countries that legally allow its production also require strict proof of age for the people actually having sex.