Bunch of crap. They're not slaves, they're people living in extreme poverty, to whom those jobs are the only way they have of getting out of it, and those self-righteous idiots are their worst enemy, because they're actively trying to remove their possibility of having a better life. Krugman's article explains it well: http://web.mit.edu/krugman/www/smokey.html
I think C.S. Lewis' quote is completely appropriate here:
"Of all tyrannies, a tyranny exercised for the good of its victims may be the most oppressive. It may be better to live under robber barons than under omnipotent moral busybodies. The robber baron's cruelty may sometimes sleep, his cupidity may at some point be satiated; but those who torment us for our own good will torment us without end, for they do so with the approval of their own conscience."
I don't know if it's inevitable, but it's only been for the last couple of hundred years of human history that it was not very commonplace.