Sometimes when I hear something really dumb from mainstream economists, it actually makes me feel better because it helps validate my own belief which is basically austrian economics.
"Inflation is not causing commodity prices to rise for a given time period because the dollar index did not fall in that time period." This is obviously wrong because the dollar index only measures the dollar agains a basket of other paper currencies that are ALSO being inflated.
"Raising taxes by x% will result in a gain of tax revenues by x%" Wrong! Behavior changes as tax rates rise. See the Laffer Curve.
"Taxing the rich and distributing it to the poor will actually help the rich by driving up demand for their products." Wrong! Needs no explanation.
Those are just a few off the top of my head.