America is also a pretty classist place, but for me the people you hear saying "it's about class, not race" are mainly working to ignore that America is a pretty racist place. And indeed, part of why it's easy to make that argument is that almost all of America's history involves racial discrimination to create and magnify class distinction. See, e.g.: http://www.theatlantic.com/features/archive/2014/05/the-case...

I'd be interested to see how the study you suggest turns out, but I wouldn't expect it to be much different; there's too much other evidence of purely racial bias.