I don't know exactly when, but I think it was from the classic Dogfart BlacksonBlondes scenes with Alisha, Kacey Kox, Violet Blue, Aurora Snow (in the sauna) and the amazing Jennifer Gold. Alisha looked like a more-attractive version of my h.s. girlfriend's best friend, who loved black men but wasn't really that cute. So I got to enjoy watching a hotter version doing anal and sucking huge cocks. Jennifer Gold was so flexible and soft, perfect kind of chubby. Aurora, Kacey and Violet need no introduction.
It wasn't the only thing I was into, but the gangbang scenes (those of the gonzo era) always seemed harder and sluttier than the other stuff I could find, usually with higher production values. So I'd watch them. It would be several years before I'd reveal that I was into it to a girlfriend, and she was too flighty to engage in it (only 18 yo) but had a cuckoldress side to her. Then I found out about the cuckold amateur community, with Holly Wetlove, Lana Love, Hotwife Tish, Cathy Craving, Gabrielle Santini, Jesse Teplo and the obnoxiously but incredibly hardcore Fetish Fun series. Unbelievably hot.
Since then, I've discussed interracial gangbangs with no fewer than 12 of my sexual partners, almost all of them smoking hot, intelligent, educated white or Asian women in their 20s. A LOT of women are into it, it's just a matter of making them feel comfortable about expressing it and handling it in the way that they want (my wife and I, for example, do not engage in any overtly racist talk; it's all about just being fucked by big thick cocks and the hard-bodied men attached to them, and black men are hot). I tend to date liberal women, so very few are interested in any kind of race play, which is my preference too.
When they know that it gets me off, they often play it up. I dated an absolutely GORGEOUS girl who sucked my cock on camera while talking about how she wanted to be gangbanged by 4 black cocks for daddy. That fantasy existed before me and exists now, to the best of my knowledge.
The last woman I was in a relationship with before my wife almost exclusively watched interracial gangbang porn. After we broke up, she tried living without home internet for awhile and asked me to download as much IR gangbang porn as I could fit into a dropbox, and she downloaded it for offline use. Every video was IR gangbang. She even found a pornstar who looked remarkably like her, and regularly got off to the video of her being gangbanged. This was a cardigan-wearing young upper-middle-class professional woman from the suburbs. To the untrained eye, she'd never come off as "one of those." But she sure is.