We have a problem in human behavior: given a choice, people will buy the least expensive product, whether it's produced in the US or China, no matter how the employees are treated. First, there's no real way to know where the whole production chain is and what company policies are. Second, I don't think in the end most people care enough to affect their buying decisions. I can understand that, particularly since many people don't exactly have money to spare.
The only practical way to protect workers is to have regulations and inspections. That way all the vendors are on an even playing field, and we don't have a spiral to the bottom. But there are all kinds of political problems with doing that, ranging from companies paying politicians to ideological objections to the government doing that.
