I'm sure the police would like to write it down in a log that a killer just walked into a room, locked the door and started shooting people one by one. By the time any security is at the scene there would be hardly anyone alive. In such a situation not just minutes matter, but seconds; and how long will it take for a group of officers to cover 2-3 miles of campus roads, enter the building and then locate room 3742A ? As I recall my university years, some rooms were well hidden by architects and generations of administrators. You can't just expect that a generic cop would instantly know where each one out of 10,000 rooms is located.
But the far more valuable effect of allowing all qualified gun owners to carry them on campus is that deranged maniacs will no longer see those campuses as their personal hunting ground. They might as well break into Camp Pendleton or Fort Knox, guns blazing, with about the same results.