The problem with the third world is not so much that wealth is unequally distributed, but that it (the third world) is not currently in a position to produce wealth the way it could. This is a problem that needs to be rectified, (and sooner or later will be,) but it is not so much a matter of social justice as of genuine philanthropy.
That said, he's right, there is a lot more that we could do to help out the rest of the world that we don't do and we should take this into account. The problem IS that the problem is so complicated; simply giving or redistributing wealth won't cut it and might even hurt matters at times. I think that we'll figure it out sooner or later.