Colorado was a terrible team for all but a few years. When McCartney became their coach, he very vocally declared Nebraska to be Colorado's "rival'. This was never a mutual rivalry, and never really serious in any Nebraska fan's mind. It was manufactured and Coach McCartney used it as a benchmark for his team and fans, an attempt to quickly elevate Colorado to Nebraska's longtime status as a football power.
There was a lot of bad blood stirred up against Nebraska, for no other reason than we were historically a much better team. They circled the game date in red on calendars, said very negative things about Nebraska in the local media, and painted us as the "bad guys" that needed to be beat down.
Colorado's fan base took up this mission, and took it too far. For the few years when Colorado was competitive with Nebraska, Boulder was a dangerous place, physically, for Husker fans. There were assaults, batteries thrown, rocks thrown, injuries. Their fans keyed cars and broke mirrors and windshields on cars that merely had Nebraska license plates.
It was really, really, overboard. And all for the sake of a manufactured rivalry based, I suppose, on envy for our program's consistent success.
When Colorado fell apart, as a program, embroiled in scandal, the "rivalry" finally disappeared. Thank God. I lived in western Nebraska and truly had concerns about just being in the Boulder area anywhere close to game days there. I never went to any games at CU during that period, but had business in the area and had to go.
Some Iowa fans, at first glance, are spewing eerily similar (and, I think misplaced), vitriol at Nebraska, seemingly for no better reason than we have done more as a football team. I hope it never develops into the all-encompassing rage that Colorado fans had, but it looks spooky close, especially given that we have only played one game against the Hawkeyes since joining the BIG.