BO in NOT a NATURAL BORN CITIZEN!
Read the CONSTITUTION!
I don't think he is, either. It was a "for sake of argument" post.
There's two avenues of argument about his status, but which one governs depends on where he was actually born. The more subtle one is that Anne Dunham hadn't been around long enough to confer citizenship maternally. The obvious one is that he was born somewhere else, and/or that his primary citizenships were British and then Indonesian.