It's a legit part of race-play sex. And as I've said elsewhere on these boards, the whole kinky taboo of interracial sex that we all enjoy so much IS founded in racism. It's twisted, sure. But that's what it is, and where it comes from. The taboo.
With that in mind, some folks like to take it to extremes. So long as all parties understand the game ahead of time, there should be no cause for offense.
I admit, I was curious after watching a few pornos where a Southern hotwife used the "n" word several times during kinky sex. The intent was to spur the black man on, and it worked very well. So, I convinced one of my playmates to call me a "n!gger" as I fucked her with the intent to impregnate her. She did not want to say it at all. I had to reassure her that I knew she herself was not a racist. Even after complying with my demand, she still hesitated when the time came. She barely choked it out, and so I made her say it again until it sounded convincing. It did work. My arousal spiked, and as I fucked her with more savage zeal, she uttered the word again of her own volition, goading me on in her pleasure.
We were adults, and we understood it was not a true testament of her character whatsoever. The woman was already raising 2 interracial ch!ldren after all. It was all just naughty fun. So, party on.