Furthermore, the only valid response to a silly assumption is a better assumption. There is no such thing as economics or any science without preconceptions about underlying behavior. People who do not outline their assumptions explicitly like economists have probably smuggled in an even sillier set of preconceptions. And one final aspect of modern economics which frustrates people, even some economists, is that the field has become extremely technical. It is often difficult to distinguish an economics seminar from a mathematics seminar.
Economists seem more comfortable speaking in differential calculus than in plain old English.
Explaining the behavior of millions of human beings must be at least as complicated as explaining the behavior of heavenly bodies in motion. And the use of everyday language may be a disadvantage when you are trying to be precise about everyday things. If you examine textbooks on economics written 100 years ago, they will be written in plain English and say many true things. But a modern textbook filled with figures, diagrams and equations conveys a much more powerful and complex apparatus for thinking about economic life. I would even argue that economics should be more technical than physics.