When confronted with thoughts on America's latent racism, I tend to remind whoever I'm talking to that these things take time. For some reason this is generally taken as racism itself -- "you're settling for the way people treat each other when you could be out there fixing it! right now! tomorrow!" -- which it isn't. It's common sense, based on historical perspective. Humans are inherently distrustful of the "Other" that you mention. This caution is biological (and exists for many good reasons), and unfortunately in the so-called civilized age it has manifested as racism and sexism and so on. So, these things take time. Defeating our own biology is a slow, painful process. Of course Dr. King's dream hasn't been realized everywhere, at all times, as an ideal. Only fools fail to understand that. But it's a different sort of fool who thinks that Rome was built in a day, or that reminding others that Rome wasn't built in a day is somehow akin to wishing Rome was a crater.