That was it. I do not fault Griffin, whose incredible background you cited, for wanting to explore the experiences of black people and "walking a mile in their shoes." White people do not need proof of their prejudice. They do not WANT proof of their prejudice. They already know, because they practice it so well. What they really do not want is some other white person calling them to task for it. They consider that sort of white person the worst sort of traitor, which is why not only he, but also his parents, for heaven's sake, had to relocate.
I've often said in my writing that there are actually more white people who would be willing to be both allies and anti-racists, but their fear of being shunned by the white community is greater than their willingness to embrace, and perhaps be enriched by, a different community. Social disapproval is huge, and, as you know, we blacks can be just as afraid. How many of us have hidden our lights under bushels for fear of being perceived as "wanting to be white?"