The capitalist argues that, because the US and Western Europe are relatively prosperous and comfortable, and because the "third world" nations are relatively poor and squalid, it follows that capitalism is better than socialism.
One could just as well laud the merits of burglary by taking a tour of two houses, the house of the burglar and the house of the non-burglar (who happened to have been recently visited by the enterprising burglar). The burglar's house would be marvellously full of loot, while the non-burglar's house would be empty: positive proof of the success and justice of burglary. Instead of complaining, the non-burglar should follow the example of the burglar, of course.
The fact is that the affluent industrial nations have mercilessly exploited these "third world" countries in the past, forcing them, by means of imperial armies and navies, to hand over their resources and to produce things which contribute to the prosperity of the colonial master, all to the severe detriment of the colony's internal economy and the well-being of its people.
The British forced the Indian peasant to grow indigo for export, when what the peasant really needed to grow, and wanted to grow, was food for his family. The same is true with coffee in colonial South America and cocoa in colonial Africa. Is it any wonder that the nations which emerged from these parasitic plantations are poor, after having had their internal economies totally disrupted and replaced with arrangements which were designed to enrich the master nation and make the subject nation helpless and dependent?
According to capitalist ethics, this is laudable conduct, and the failure to be equally ruthless is a transgression worthy of punishment, and the just punishment for not having the heart or stomach for this violence is a lifetime of grinding poverty. It is quite obvious why the capitalist apologist is devoid of any coherent concept of ethics and must hold human life to be cheap.