Back in the 80's they argued that women were being forced into porn. As evidence, they paraded around Linda Lovelace, who by most accounts was crazy as a shithouse rat. She claimed she was forced at gunpoint to do porn. Other porn actors and actresses said she was a freak who would do anything sexually, including bestiality. The very best they could claim was a case of consent being removed after the fact.
The argument hasn't changed much really. Now the big thing seems to be sex trafficking, and feminists claim that many (if not most) sex workers are being forced into it. The problem is that there's no shortage of women who want to work in the sex industry, and criminologists can't seem to find all these women they claim.
Ronald Weitzer, a criminologist at George Washington University and an expert on sex trafficking, said that trafficking is a hidden crime whose victims often fear coming forward. He said that might account for some of the disparity in the numbers, but only a small amount.
"The discrepancy between the alleged number of victims per year and the number of cases they've been able to make is so huge that it's got to raise major questions," Weitzer said. "It suggests that this problem is being blown way out of proportion."
http://www.washingtonpost.com/wp-dyn/content/article/2007/09/22/AR2007092201401_pf.html