I’m a physics student. My studies, research, and ultimately my career relies upon facts. If I were to publish a paper with incorrect*, falsified, or made-up facts, I would be discredited and my reputation seriously tarnished.
I’m not sure what sort of student Ms. Clymer is, but I’m pretty sure that facts are important to her course of studies as well. In in a letter to the editor of the Arizona Daily Star, she claims,

In the hands of ordinary citizens, guns do more harm than good.

Since a picture is said to be worth a thousand words, I reply thusly:

In short: Prove it. The evidence certainly seems to favor the opposite conclusion: there are 80+ million gun owners in the US, with hundreds of millions of guns. A not-insignificant number of these gun owners routinely carry their guns on a regular basis with essentially no statistically significant negative effects.
It certainly seems that guns in the hands of ordinary citizens do not, in fact, cause more harm than good. If they did, there’d be some significant evidence of this…and, as far as I’ve been able to find, no such evidence exists.
“Gun-free” school zones have been implemented on a widespread basis across the country. There have been several high-profile acts of violence at schools over the last ten years or so. Maybe it’s time to try something else
Even if allowing law-abiding private citizens to be armed on campuses doesn’t reduce the overall rate of violent crime, it’d at least give folks a fighting chance to defend themselves from violent crime. Given the overall good behavior of concealed carry permit holders, I don’t foresee any particular downside.
* Assuming that the correct information is presently known. Science is always advancing, and it’s quite possible for a hypothesis to be shown to be wrong in the future. If this occurs, a new hypothesis is created. In general, this does not reflect poorly on the author of the incorrect hypothesis.