I believe boredom makes people vulnerable, easily distracted by anything presented to them in a convincing way, including white supremacist doctrine. Your people have profited from the enslavement and persecution of nearly every other race, and will continue to do so. You might grow up believing everything will be handed to you, or that you will only need to do a minimal amount of work. This is at least the common assumption of the middle and upper classes. People act out violently when they feel powerless.
Rage is a last resort when the buttons have been pushed too hard and too many times.
Whites are no longer the majority everywhere in America. The white race does not dominate in cities in New York, Texas, and California. This could be intimidating to someone who is used to dominating everything everywhere. Imagine a white man who has the skills and training needed for a particular occupation, is turned down, and sees the job given to a black woman. He feels like a failure.