I did go to ISU, for academic reasons, not to follow an athletic program. I also met lots of ISU students who did the same thing, all the while staying loyal to the Hawkeyes.
And why do ISU fans care so much about whether or not fans are students/alumni? A large fanbase is a good thing, regardless of whether or not they went to college. Their money and loyalty is just as good as an alumni's.
Makes you wonder why they were Hawk fans in the first place. BANDWAGON. I bet you cheer for the Yankees and Duke, too. It's COLLEGE athletics. Generally you're supposed to cheer for YOUR OWN COLLEGE. Not the arch rival down the road. If you're going to Iowa State and you cheer for Iowa (and didn't previously go there), you should probably question why you cheer for them in the first place...