The point is that an equilibrium is allowed to form between defenders and would-be attackers. More attacks, more people start going around armed. Silly no-gun zones only frustrate that process.
More people going around armed is generally a good thing for reducing crime. I don’t have statistics but I have been enrolled in 4 CHL/renewal classes. I have seen a total of two 21 year olds in those classes. My son was one of those. I think that even if CHL were allowed on campus the number of students who would be eligible to carry would be very small. There would likely be more school employees taking advantage of it than there would be students. That does not change what you posted, it is just my empirical observation.