David Friedman (anarcho-capitalist)'s comment on market failures is that they do happen, but what might be called government failures also happen, and are probably a worse problem.
"Individual actors usually receive most of the benefit and pay most of the cost of their actions, making market failure the exception, not the rule. On the political market individual actors—voters, politicians, lobbyists, judges, policemen—almost never bear much of the cost of their actions or receive much of the benefit. Hence market failure, the exception on the private market, is the rule on the political market."
Of course, Cowen is also a market actor. So, I'm not sure where the inconsistency lies.