“If the nutbar went off because of someone’s grading system then that’s what set him off.”
There’s NO evidence whatsoever anywhere that this is what set him off. NOBODY has found any single reason. And the stuff he left behind was incoherent rambling.
Actually, that's not true. It is quite clear-- from his very coherent communications-- that Nikki Giovanni --intentionally or unintentionally-- set him off.