A lot of it falls down to what you can do about the practices as well.

If it is discovered that a company in the States, or another developed country, is doing something like child labor, then you can report the company to the authorities and it can be shut down.

What will you do in less developed countries? If you report it to the local authorities, they will just look at you funny and say So what?

So, you exercise your market power and refuse to buy from that company. You even get other people to do the same. What happens then? Let's say your actions actually manage to shut down the local company that commits the offensive practices. What little money the people were making is now gone, so they either starve or go to work at another, similar company. You inconvenience a few fat cats and the workers starve.

Unfortunately, there is nothing black and white about these situations. A person can only do what they feel is best.