Honestly, given that Gary Gygax himself identified as a member of one of the many real world religions that categorizes humanity as inherently evil (with some saying that humans also deserve neverending torture or complete annihilation in the afterlife because of this), I'm a little bit curious if Neutral in D&D is supposed to actually be Evil and Evil itself is actually "very Evil".
Making other non-human races in D&D more predisposed to Good implies that humans are inherently morally inferior in comparison. Elves and dwarves traditionally weren't killing humans, but usually they had their own lands, possibly as a way to keep themselves away from the comparatively morally inferior human species.
Plus there was that one 3E book that introduced a god of humans whose alignment was Lawful Evil.