The answer is that "these people" know and understand at some level, even subconsciously, that if they acknowledge and allow the true history of how they came into such immense wealth and power while everybody and anybody who "does not look like them" have been forced into abject slavery, neo-slavery, colonialism, imperialism, poverty, misery, and pain....then "these people" will have to face the fact that their wealth and power and security are based on murder, rape, robbery and genocide.

They'll have to ask anybody who will listen, but mostly themselves: "You mean, my great, great granpa and grandma did THAT?!

Then what? Well...as a friend of mine once so succinctly put it, "When white people steal black, brown, red and yellow folks' stuff, it stays stolen."