Well I don't have time to read the whole ongoing discussions so my point is probably already made. Anyways:
I think it's easy to insist on human rights when your well-being is not threatened.
Moral values, whether 'natural', religious or legal will keep one from putting into place immoral or unethical practices, but there has to be a tipping point for anyone. The exact moment of tipping will obviously depend on the individual, the situation and the moral rule that is to be infringed.
Take the example of concentration camps. The idea that all prisoners would cooperate and help each other out is totally wrong. People often tried to get favoured treatment by telling on others, or stole food from one another. I would say that's immoral, but would I do the same if I was dying of hunger or, worse, seeing my child die of hunger in front of my own eyes? Yes.
I guess the opening question is designed to make one realise this. I think it's fairly impossible to answer a priori to where my personal tipping point is for enslaving people, but it's clear it exists, no question.