I don't know much about economics, but when I read stuff like this I get the idea the author doesn't know much more than me. There are a lot of smart people in economics who talk about inequality being a serious issue, for reasons that Paul Graham probably doesn't understand. There are probably also people who use the fact that economists agree that inequality is bad as an excuse to demonize all rich, successful people. Some of them are on my facebook feed, and they're annoying. But those people aren't the experts, and somebody making a bad argument for something doesn't mean there aren't good arguments for it.
And the "blogger claims entire field of study outside his own area of expertise is wrong" type of article always fails the sniff test, no matter what the subject material is.