Once upon a time, the fountain had been simply known as "the fountain," but around 25 years ago, it was unnecessarily renamed after a controversial person.
The reason for the renaming was the same as with any memorial or monument designed to honor a person or idea — to create an emotional connection and familiarity with the person or idea connected to the place; to communicate a certain view of history.
The renaming of the fountain followed an earlier renaming controversy. One of the University's dorms, Nichols Hall, was named after a participant in the infamous Sand Creek Massacre. Even in its own time, the massacre had been denounced, earning condemnation from Indian fighters like Kit Carson. Not surprisingly, the dorm that bore Nichols's name was eventually renamed "Cheyenne Arapahoe" in honor of the Indian tribes whose members Nichols had helped attack.