The US believes the constitution ends at its borders and people; This is what the law is in SA.
I can't say I like it either, but I think jailing human beings and enslaving them to the benefit of others is simply not Good.
If you can agree then maybe we can work together to fix it in the US in a lifetime or two, but there's frankly little we can do about SA if we can't show the world what being Good looks like in America.
Morality isn’t a game of brinkmanship. It’s incumbent upon each country to improve itself, without resorting to their peers’ moral failures as a cheap response to observations of their own failures.
https://en.wikipedia.org/wiki/Burj_Khalifa#Labour