...we all know that in all matters of mere opinion that...

...we all know that in all matters of mere opinion that [every] man is insane-just as insane as we are...we know exactly where to put our finger upon his insanity: it is where his opinion differs from ours....All Democrats are insane, but not one of them knows it. None but the Republicans. All the Republicans are insane, but only the Democrats can perceive it. The rule is perfect: in all matters of opinion our adversaries are insane.