Yes, the war on drugs is an effect, and racism is the cause. If that's what you're saying then we agree.
But on a practical level, the war on drugs is the means by which institutional racism is most likely to be prosecuted in this country. So to some extent many racist acts are the effect of the racist war on drugs.
Perhaps a distinction without a difference. Clearly our drug policy and racism are deeply intertwined. Many do in fact disagree with that or are ignorant of it.