If I am in the mood for boneless wings and a cold beer, I go to BWW... Why? because their boneless wings and sauces are superior to other places in Ames. That being said, Yeah its probably going to **** people off to see girls in Hawkeye gear, but its their freedom.
They will suffer the consequences most likely by seeing reduced tips, A good manager would realize this, But really cant do any more than say, Hey I realize everyone has opinions on favorite teams, However this is Ames, and It would be in your strongest interest to refrain from wearing items that may reduce your own, or the restaurants profit making capability.