Flippant, not correct comment: Didn't that start way back in the mid-2000s with Asher Roth? He's the first memory of a rapper I have where my friends moms were okay with the music. I wouldn't be so quick to attribute to being a racist though, most of the people I've seen that talk about Macklemore or similar artists just don't care that much about music and like him because he's easy to digest, and they didn't have to work to find his music. It's the surface, lowest common denominator artist at the moment.
True enough. Born out of ignorance than anything else. And yeah, it kinda did. Asher, Eminem. The Beastie Boys, if you go back far enough. Vanilla Ice. But Eminem got Dre's stamp of approval in 1999, so he's a little earlier than Asher. My favorite, though, is MC Paul B. Got quoted as making "the whitest EP ever made" by NYT.