You guys should all consider
reading this article on the topic by a guy named Justin Slayer, one of the bigger black-male names in the mainstream industry. Its long, but speaks to the topic perfectly.
It is true that for some girls, IR porn is avoided in order to maintain an image. They may appeal to a certain type of (mostly white) audience that doesn't particularly care to see them with black men.
But I generally don't buy that A-list porn starlets will usually turn down black men, and that doing black men hurts their chances to progress and become said A-listers in the first place.
A-list names(or names who were hot at the time) that have done IR so far:
Sasha Grey
Tori Black
Lexi Belle
Charley Chase
Jenna Haze
Rebecca Linares
Eva Angelina
Bree Olson
Naomi
Stoya
Tanner Mayes
Kagney Lynn Karter
Brianna Love
Hillary Scott
I could go on. You can find the names of popular/nominated starlets
here and
here. A quick google search will reveal that most of the recent ones have done IR, and it has not hurt them.
As I said, though, racism is still real. Some popular contract girls (Kayden Kross and Alexis Texas, to use more notable recent ones) will openly refuse to do it, and a lot of their companies won't let them.
Personally, I don't really watch mainstream american porn as it often appears too artificial to me(I stick to foreigners and amateurs). Regardless, I couldn't care less if one silly little porno-chick swears off of black guys. For every one of her, there are plenty of other starlets who will do the opposite, and even date/fuck black guys in their personal lives(Charlie Sheen's goddess is one of these).