No doubt, they're not going to turn down someone wanting to buy their product. But they are going to market it to the tastes of the majority of their target market. Much like your local grocery store. If you go to a grocery store, it is setup to cater to those in the area.I basically thought much of the same thing when I first heard the news. It may pay off long term.
One thing though is a lot of parents buy Nike products for their kids. Many of these parents my decide to look elsewhere and get their kids hooked on some other brand.
For me, once I find a shoe that fits, functions, and lasts the way I like it, I don't usually look to change (basketball, running, tennis and racquetball). I tried a Nike basketball shoe a long time ago and I didn't like it so I've never bought another Nike shoe of any kind. From a marketing standpoint, if anyone switches from Nike or tries a non-Nike shoe and like what they found, they may not buy a Nike shoe for a long time. This is one area that may backfire on Nike's long-term plan. I don't think I fit the big dollar purchaser that Nike is after anyway.
I think the demographic they are going after is the kids/young adults as you mention but includes whites just as much as non-whites.
Funny, but true story. I am an avid bbq'er (aka "BBQ Snob") and am very picky about certain things when it comes to the meat I decide to smoke. One of those "certain things" is when I cook pork ribs I like cooking the whole untrimmed spare rib. I do not like buying ribs that have already been trimmed. For me to consistently get the whole, untrimmed spares that I like smoking. I have to go to a grocery store in a part of town that is predominantly black. "Predominantly black" meaning I'm the only white thang up in there. LOL! Every time I go in they already know what I want and call back to the back before I even get back there telling them I'm coming! LOL! Great service. But, the grocery stores in the area of town I live (which is predominantly white) do not carry the whole spares. Because people in that area do not buy them. They prefer St. Louis trimmed spare or the baby backs. Which is common with white folks. Just not this white boy.