I have discovered that, apparently, a pat on the head and smiling at them before walking away is not considered polite.
I Have the Same Question
The View From North Central Idaho
Ramblings on explosives, guns, politics, and sex by a redneck Idaho farm boy who became a software engineer living near Seattle.
There is no polite way to disabuse them of their ill-considered notions.
Politesse is not effective – blunt force trauma to their worldview is the only reasonable measure.
I suppose that if the interlocutor is deemed to be possibly salvageable, giving them a copy of Economics in One Lesson might be worth a try Giving them a copy of The Virtue of Selfishness is probably only useful as a second step.
Kurt