Oh, I get it.
If I had a time machine and went back to witness an Aztec sacrifice, I might not be the hero by single-handedly trying to fight off hordes of thousands (and quickly be killed in the process or risk being sacrificed myself, not to mention potentially changing history & reality in ways no one can imagine by interfering with time), but at the same time I wouldn't cheer with the rest of the crowd.

There are many factors and mindset is one. They are taught at a young age, meaning the villagers, that this is normal. Most of the people who were sacrificed were prisoners of war. And when they weren't available, it was by lot. This was practice by the Druids, Vikings and Sumerians, as well as other cultures who believed in human sacrifice.
Also, we can view this like kamikaze pilots of Japan. They are "taught" it is better to die at your own hand than to die at an enemy's hand.
Or go watch Robin Hardy's The Wicker Man.
I guess I'm the only person who sees in ancient cultures, the was normal.
I guess as much as I study history and early cultures with torture and sacrifice, I don't see an issue.
AND, You have a modern mindset, not ancient, so you find this wrong . It's only wrong by modern standards.
Remember, there are non Modern religion believers.