I liked this joke from the comments section at the MR site:
Have you heard the joke about the chemist, the physicist and the economist who get wrecked on a desert isle, with a huge supply of canned baked beans as their only food? The chemist says that he can start a fire using the neighboring palm trees, and calculate the temperature at which a can will explode. The physicist says that she can work out the trajectory of each of the baked beans, so that they can be collected and eaten. The economist says, ‘Hang on, guys, you’re doing it the hard way. Let’s assume we have a can opener.’
That’s what a lot of modern macro is today – ivory tower theorists explaining to everyone else that their ideas are right because they made the math work in the model that they made up. And so long as they have a PhD the rest of us feel obligated to give their ideas the time of day no matter how little the model resembles the actual real world. Fun times.