Mark Waid is wrong. Miller's Batman has always had a right-winged streak to it. He takes a hardcore right-winged approach to crime (Miller's Batman focuses on mobsters, drug dealers, pimps, the government, etc.), he fights against the oppressive and corrupt police forces, never trusts the government, the government is portrayed in an Orwellian fashion (particularly in the Dark Knight Strikes Again), and his Batman speaks like Clint Eastwood, who is a hardcore libertarian (you can even say that Grant Morrison took that to an extra extent by making Bruce Wayne act like Eastwood).
Frank Miller is a hard core right winger. He makes George W. Bush and Ronald Reagan look like a bunch of ***** liberals in comparison. That's where is criticism of those presidents come from. He got a lot of **** for his rather rude criticisms of the Occupy Wall Street protesters and his blatant Islamophobic beliefs.