It is almost laughably easy to criticize the models of political science and economics. They are always reductionist, littered with obvious exceptions, and describe the past rather than the future. But since we can't get very far without making assumptions, we are willing to suspend disbelief and assume things, even concepts that are obviously incorrect. So the assumption that people are rational perseveres. After all, there are infinite ways to be a moron, but only one way to act rational (or so they say).

Because of this modeling fetish, many obvious observations that can't be modeled never enter into the economic/political science canon, while many dubious models persist simply due to elegance. 

That's why I love that Larry Summers (by all accounts an arrogant prick) once began a paper attacking efficient-market (i.e. super rationalist model) theories with this line:

"THERE ARE IDIOTS. Look around."