Not the OP, but I think the argument is that even if they're doing it for the wrong reasons, it might still end up being a good thing.
What kind of logic is that? It reminds me some people I know that vote to extreme-right parties because "well, we know that the regular parties are not gonna change anything. These new guys may do something new. Who knows, let's vote them and find out"
A core assumption of capitalism is that when individuals act in their own self-interest, their actions tend to produce outcomes that are beneficial for society as a whole. This seems like a compelling piece of evidence!