I gotta ask, if its just an average black guy with a dick size and build similar to the MC, is it till part of the blacked fetish?
I would say no. I think for people who enjoy the fetish, there must be reference to the color, that it's big, and that he is superior in every way.
similarly, is it still blacked if its a stereotypical steal yo girl black guy but no one mentions him being black or his dick being big?
Difficult to say in this scenario, but him even being depicted as "steal yo girl" instead of "steal your girl" is leaning in that direction. I'm not sure if that's a big part of the fetish, but it seems that way. That or developers don't realize that there are educated black men out there and aren't all villains. Basically, I can usually tell if it's going to be BBC/blacked by whether or not the BBC lovers posting in a thread seem like they're happily frothing at the mouth.
and would it still ruin it for you if it was the same thing but with a white guy?
You mean if it was a white guy stealing from a black guy and the girl would instead scream something like, "Yeah, give me that big white cock!" I'd find that quite weird... just say "big cock". Why does the color have to be mentioned? But that seems to be part of their fetish.
Of course, these are merely my observations based on many NTR/NTRS games that I've played and how the fan base of that particular fetish react. But maybe there's something more to it. Looking at the request by Yougiblack, he specifically asked for a big black cock. If dev instead put in an average black man, I think Yougiblack would be disappointed. But I guess only he can answer that.
