My wife used to work for the US government on combating human trafficking, so I know something about the subject, at least secondhand.
It's absolutely true that the conditions in China and many other countries are abusive in many if not most factories--long hours, low pay, etc. And the environmental protections are nil.
What muddles things is that the alternative for these factory workers is often prostitution or begging. In poor countries that have very little manufacturing, this is often the case. If it was your 9-year-old daughter, would you prefer that she be sewing for 12 hours a day or working as a prostitute? Because *those are the choices* over there, like it or not. We can and should try to change that, but in the meantime, it's good these people have jobs.
I think that improvement in conditions will come gradually, with political pressure from other nations. Remember that the US had some pretty awful textile mills in the 19th century. (I'm not going to compare child labor in China with slavery in the US, because there simply is no comparison. That would be gauche and inaccurate.)
I used to avoid buying Chinese-made goods until I realized the reality of the choices over there. And I still lean toward buying things made in more developed countries--but to be honest, it's mostly for selfish reasons. I simply believe (perhaps wrongly) that a snowboard made in Austria is probably better made than one made in China. I have nothing to base this on, and I might well be wrong. After all, US automakers are paid better than any in Asia, and who makes better cars--GM or Toyota? (Yes, Japan is more labor-friendly than China, but I'd still bet that a Chinese-made Buick is better made than a US-made one.) I will say that I regard China as a very evil country for its oppression of political dissidents, its support of the truly Orwellian military junta in Burma, and its ongoing financial support of the Sudanese government. But not buying goods made there isn't going to change anything.
Anyway, despite the horrific conditions in these factories, the people who work there are actually glad to have those jobs. I wouldn't want to flip burgers down the street here, but I'm sure the person who does that is glad to have the job rather than no job, or he wouldn't be doing that. If you feel guilty buying something from China, then donate some dough to UNHCR, Amnesty Intl, MSF, etc.
Sorry for the ramble!