Have you ever been to the Chinese countryside? I have, my wife is Chinese. My wife's sister is disabled and married a man from the countryside, a common arrangement in China, so I have relatives from the country. Trust me, sending all those workers back home really isn't going to do an awful lot to reduce human suffering. They choose to go and take those jobs for good reasons.

Many of the workers in those factories are women. After a few years, they often go back home as the wealthiest members of their families, with enough capital to build homes and start new businesses of their own. It's actually started a distinct demographic trend. People have all sorts of bizarre ideas about china. Sure the conditions in these factories are awful by western standards, but China isn't the west. The same basis for making decisions just don't apply. Hopefully they will one day, but we're not there yet.

It's all perspective, just like (paid) child labor in some cultures. While west europeans and most north americans oppose child labor and slavery, in some countries and cultures it is only the 'lesser evil', compared to sex slavery/prostitution, starving to death or getting maimed to then beg for some pimp type of situation.

Is the human assembly line ideal? No. But for many workers it seems that the alternatives in the rural areas are either non-existant or pretty bad.