Is this guy really this stupid or is he on drugs?
Or maybe he doesn't care what other people think. Unless Iowa redistricts his seat out of existence, there's no sign his constituents are going to turn their back on him (the left tried like heck to take his seat this past cycle and failed). So, what incentive does he have to back down?
Certain people would rather stand tall on a dumb idea than back down and be seen as weak.