In the Vietnam War era, America was troubled over its own capacity for violence and dishonesty. The figure of the zombie was the perfect open-ended metaphor for the new domestic threat. You didn't know who they were, where they were or how many there were, only that they were coming at you from all sides, and some of them looked just like you. The black hero is smarter, richer and stronger than his white counterparts. The government is impotent.
Brothers eat sisters.
Daughters eat parents. This has resulted in better and better video releases. Every other change, though, is ruinous. The content of any film, however, exists between the script lines, and that is exactly where Russo unleashes his kamikaze editing style. Turns out, he's a recently executed child-killer set to be buried.