Do you think they didn't? That attitudes prevalent about segregation in, say 1950, are equally as prevalent and as strongly held today?
What about the forced integration of the US military? Do you think prevalent attitudes today about something like white soldiers serving under a black officer may have evolved a bit from the prevalent attitudes of pre-integration soldiers?
We're getting way off course. The military's handling of segregation is irrelevant to the discussion. There's no where near the same possibility for natural social evolution. I'm not saying that forcing people to interact with each other won't eventually affect how they view each other. I am saying that I doubt the Civil Rights Act of 1964 is directly and singularly responsible for the progress we've made. You can't force people to like each other. Generations later, race relations are better. But some people still hate people who don't look or behave like them and they always will.