Saying "generally" doesn't make it not ignorant or not a stereotype - in fact I'm pretty sure its just the opposite. "Generally, people in the midwest are beer swilling, liberal bashing layabouts" is pretty much the definition of a stereotype...
There is certainly nothing wrong with working at a time of day which is most productive for you, but the implication was that midwesterners were generally unwilling to put in a bunch of extra hours to "get it done." Not that they frowned upon people who liked to work at night.
I would argue, pretty strongly, that the culture of "kill yourself working a billion hours a week for your startup" is unhealthy physically, socially and mentally. Sure there is an outside chance that you hit it big and get fabulously wealthy. In the mean-time you pass up tons of actual real-life salary, benefits and vacation time that are tangible, usable, and increase your quality of life today. (Not to mention an actual retirement account, which most startups seems to neglect.)
