It's a BS theory, why wonder when it doesn't behave like a rational theory?
That's why it's possible to make pretty movies about times long past in (e.g.) white empires, starring not-so-bad members of the "racist" social groups. They give candy to the poor little untermensch offspring, upping their karma because despite their active (or not) affiliation with said group, they are "good" and pretty for the movie.
It's a cliche, but one blurry enough to apply to many.
I hate your filthy guts, but once you give me your land, I'll make compassionate fashion trends in your image.
Like Frenchy said, when the brain stops, the insults start.
You could have colonization without racism, the same way you can impose martial law without diktat being your end rather than just your mean.
It's impossible to control someone without first putting him in the position of not being able to not depend on someone else.
grammar edit.