Watched MF4 earlier and while I agree with the posters above I don't find MF4 fits into that category.

I find producers like Facial Abuse, German Goo Girls and Maximum Hardcore to be pretty objectionable, they aren't sexy, arousing or enjoyable to watch. as a result I don't watch them. on the other hand With MF and Kink.com in particular, I feel that the Girls are in on it are consenting and ultimately enjoy themselves, the movies always finish with a smiling girl, and that increases my enjoyment of those movies massively.

It is perhaps a very fine distinction and utterly subjective but for me it is where the line lies.