“There’s no grays, only white that’s got grubby. I’m surprised you don’t know that. And sin, young man, is when you treat people like things. Including yourself. That’s what sin is.”
“It’s a lot more complicated than that—”
“No. It ain’t. When people say things are a lot more complicated than that, they means they’re getting worried that they won’t like the truth. People as things, that’s where it starts.”
“Oh, I’m sure there are worse crimes—”
“But they starts with thinking about people as things…”

from Carpe Jugulum, by Terry Pratchett
It’s a basic point of ethics, as Granny Weatherwax so aptly puts it. Treating people like things is where the downward path starts. When a whole half of the human race is treated as things by the other half, and it’s so pervasive, so seemingly permanent that it seems like that’s the only way the world can be—well, that doesn’t make it any more right. It just makes it hegemonic.