Yup, that's the dirty little secret I found out when living in NC. Whites and Blacks get along just fine in NC, Blacks and Mexicans? Not so much.
In fact, the only blacks I deem racist against whites, frankly tend to be the lighter-skinned ones, who tend to want to prove to others that they really are black by being so anti-white.
I think it varies by region. Here in Maryland it is whites who wear the largest target.