"In its report, Apple revealed the sweatshop conditions inside the factories it uses. Apple admitted that at least 55 of the 102 factories that produce its goods were ignoring Apple's rule that staff cannot work more than 60 hours a week."
Social safety nets aren't the same everywhere.
Either those children working is a bad thing, or it's not. If they're making money necessary to feed themselves and their families, then you should be proud of paying part of those money.
Of course, we don't really know if it was a good thing. We don't know if they were 17 or 10, whether they really needed the money or how many hours they worked. The situation is much murkier then the knee jerk "I can't exploit it". And unfortunately not trying to think more about it doesn't help those kids one bit.