Lots of racist feel even more anger toward members of their own race who embrace other races than they do for the races they hate. Can't say why but since that level of racism usually stems from deep personal self worth issues my best guess is a combination of a feeling of betrayal and self hatred.

Second trying to rationalize the actions of the crazy is misguided virtually by definition. Sort of like weighing the weightless. You can study the disease but you can't use rational arguments to explain irrational actions.