Nietzsche's Other Idea
Nietzsche had a special hatred of the "slave morality" which valued compassion for the poor and oppressed. He attributed it to a sort of conspiracy against the strong, perhaps due to the Jews. He saw the mob rising against the mighty hunter or conqueror. It's a fact that our closest relatives, the Chimpanzees, tend to be very hierarchical, with the Alpha male being not so much a leader as the biggest bully on the block.
Human hunter-gatherer societies aren't like that. Instead they are highly egalitarian, without chiefs or subordinates. How did this transition happen? Nobody knows, but there are some clues, including the fact that given the right circumstances humans do form hierarchies rather easily. The biggest clue, though is the way hunter-gatherers deal with those who overstep and bully and dominate. Gossip and shunning is step one. Sometimes the offenders are driven out. Egregious offenders are killed. Haidt discusses the case of a Bushman who was executed by the community after killing three people. Men fired poisoned arrows into him until he "looked like a porcupine. Then, as he lay dying all the men and women stabbed him with their spears to make it clear that it was a community decision.
The most popular theory holds that when humans developed tools, and language, and became hunters, it became impossible for a bully, or a bully and a confederate to dominate the group. Spears, language, and cooperative hunting techniques make bullies very easy to dispose of.
This has some resemblance to Nietzsche's notion, only it developed when humans became hunters, and learned to speak - and long before slavery and slave religions.