I have a theory on this.

The ones who get the most flack for doing IR are ones that the racist white porn fans consider more "attainable".

I'm talking the pretty / slightly pretty / above average porn girls. Not the total knock-out, porn super-star, "she's so hot it doesn't matter"-type.

When they see the girl-next-door / blue-collar / white-trash princess types doing porn, they can fantasize about getting to fuck this girl they knew from the neighborhood, from school, at church, etc.

She was the hot "slut" that they never got a chance to bed.

Not so for : Sasha Grey, Phoenix Marie, Super-hot euro sluts, Lisa Ann, Julia Ann, Remy Lacrioux, Gianna, etc. These women are so hot and deliver so much sexual heat that it makes them almost surreal. They are detached from reality. Not real people. Not attainable. Not date-able. They only exist in video-land as paragons of super-sluttiness. These same racists are able to enjoy their work and give them a pass on IR because in their eyes they're not even people. They are these mythic "uber whores".

No. It's the somewhat-pretty, slightly above-average girls that do it for them. I'm talking Taylor Rain, Sarah Stone, Brandy Talore, Tera Patrick, Jeanna Jameson, Vanessa Lane, Rikki Raxx, Christy Mack, etc.

Part of keeping these girls desirable is for them to maintain a certain of level of "purity" in the racists eyes. No sex with black men seems to be a key rule to follow. If one of these formerly coveted "attainable" starlets goes to IR -- that is when you see the blacklash. The nasty comments, then, are a very emotional reaction to having very personal fantasies trampled upon.

In real life, a good number white men lose interest if they know a girl has been with a black guy. The reason for this is deeply rooted feelings of sexual inferiority to black men. "If this girl has been with a black guy, how can I satisfy her?".

So much of racism and white supremacy is sourced from this very real sense of sexual frustration that dwells white men. But that is another topic.