I don't buy that argument. It is still an emotional cop-out. Your concerns quoted here are no different than situations that could happen at malls, stores, the pizza joint, or anyplace else in public where concealed carry of weapons is legal. No different what so ever. So once again, if you delete school/university from what I quoted above, and substitute in "mall", "store", etc, do you still feel that way about people carrying firearms? There's an equal chance of someone going off the deep end anywhere else as there is in school.

It shouldn't be too hardto tell the difference between someone who is randomly and deliberately shooting at innocent people versus someone who is acting to stop the "bad guy". After that guy is stopped, put your weapon away. Pretty much just like you would if you stopped a shooter in the mall or a church. The ballistics of your weapon and the shooters weapon will be checked, they will determine the guy you shot was shooting people, and you will be good to go if you're legally able to have the weapon at the location you had to use it. That's not to say you won't need a lawyer, but you will walk if the evidence points to it being self defense. When the shooting is over, nobody is going to rush in and start shooting eachother. It just doesn't work that way.

Again, I reiterate, if people are able to qualify for a concealed weapons permit, they should be qualified to carry it whereever they may legally be with a possible exception of heavily secured areas at which they can check their weapons and pick them up again when they leave. If a place is willing to do that, to guarantee security on a building, fine I guess. I just don't see universities, colleges and so forth going for such a plan.

Actually, a good many crimes are prevented daily just by the presence of firearms. If you were a criminal, or deranged and wanted to harm as many people as possible, would you go to an area where literally hundreds of people couldalso have guns, or would you go where nobody can legally have guns? Most criminals are not stupid, nor are they particularly suicidal. Occasionally you do run into someone dumb or crazy enough to deliberately strike where people are armed. It's not often though. I submit that the presence of firearms or the possibility of presence would at least help as a deterrent. If the deterrant wasn't enough, at least we probably won't have to see 30+ people dying in an incident because police weren't able to get there in time.

EDITED TO ADD:

I forgot to address the prevention versus response. I do understand what you mean, in that it would probably be better to prevent something from occurring versus having people ready to put the shooter down after he/she starts. One problem with prevention is the economics and simple scale of the situation. I don't think the majority of people would be willing to submit to a daily search of their person or their effects (bag, etc), even if by metal detector. Do you know how many entries and exits these buildings have? They would have to either close a bunch of entry/exit doors permanently, or put metal detectors and armed guards at each and every entrance and exit of each and every building on campus. The economics of the situation are going to prohibit that.

Now the school might try a few "feel good" measures that don't really help anybody's safety, but short of armed guards and metal detectors at every door in every building on campus, they cannot sufficiently guarantee nobody will get in there with a weapon. As a result of that, the only reasonable solution is to allow individuals to be responsible for our own self defense.