If they were really selfish, they would get on with making money instead of arguing passionately with others.

This I do not understand. People are built of many different modules, and I don't see why someone can't be selfish in their life decisions, and at the same time, like so many humans, be prone to arguing about their views with other humans in spare time.

I'm clearly missing something, because I also can't see what that whole paragraph is doing in this article, what it contributes to the overall point. If anyone can be bothered to clarify, that'd be appreciated.