People weren't horrified about cruelty against slaves not so long ago, and look at where we are now. I bet most people of that era would not believe we'd ever reach the point we got now. I bet many would even be willing to die on wars for over their now-completely-unacceptable ethic standards.
That is a pretty bad example as what we have today is not much better, it's just hidden in poor countries. "Being horrified" is something most say they are and then they go buy clothes made by people living a life as bad as slaves used to.