I'll concede that you may have a point. I have not studied in depth the mindset of those who engage in these mass-murder sprees, as differentiated from ordinary criminals and serial killers (whom I have studied).
Possibly they are not deterred by the presence of armed persons, as a general thing. Possibly the reason these shootings tend to happen in places where the majority of the victims are unarmed is chance... I'm willing to entertain the idea at least.
But, let's consider some mathmatics.
If a University has 5000 students, 500 teachers and staff, and 5 campus police officers on duty, and only the five campus cops are armed...that gives us 1 person in 1,100 who is armed. This would tend to give a mass-shooter a pretty good array of victims to kill before an armed person arrived on the scene to stop him, unless he were careless or unlucky enough to blunder into one of the five cops immediately.
Now lets say that those with concealed carry permits are allowed to carry on campus. This means those who are 21 or older and have completed the required background checks, range score, written test, etc...responsible adults who cared enough to jump through all the hoops.
Florida has a population of about 18 million. Of these, about 1.2 million have concealed carry permits (CCW hereafter).
(source Concealed carry in the United States - Wikipedia, the free encyclopedia
That is a percentage of about 7%.
The hypothetical university above has 500 staff. It has 5000 students, of which let's assume 1000 are 21 or older (just a reasonable guess, 20%). That gives us 1500 adults, at 7% means probably 105 CCW holders.
105 CCW holders, compared to 5 campus cops. Now let's cut that number; in my experience about half of CCW people actually carry on a daily basis, so let's say only 55 are actually carrying at the time of an incident (assuming it was lawful to carry on the campus...in most states it isn't.)
If the would-be mass shooter has 5 armed campus cops to avoid, he could rack up quite a body count before being stopped...as witness Virginia Tech. If he had 5 cops and 55 armed CCW citizens (the latter being hidden among the general population, their weapons being concealed and them not in uniform), we just increased his chances of being stopped early by 11 times...that's a 1,100% increase.
The odds that among the first 20 people to encounter the mass-murderer, there will be a campus cop are one in 55. If we factor CCW into the equation, the odds become 1 in 5. Bear in mind that at VAtech, many people saw or heard the shooter without getting shot, mostly by hiding, barricading a door or running away. The likelihood that this guy could walk around shooting dozens of people with impunity as happened at VA just decreased eleven-fold.
I'm not talking about deterrence effect here, really. I'm talking about someone putting a 115-grain hollowpoint thru Mr. Mass Murder's brainpan and ending him right there.
Personally I think it is well worth legalizing CCW on campus, not only for this reason but because of the right of responsible, law-abiding adults to bear arms. The vast majority of universities recieve public funds to some degree; this makes them liable as "a public institution" does it not? Then a public institution should no more deny responsible adults their 2A rights than it should their 1A rights.
Fiddling While Rome Burns
Carthago Delenda Est
"I used to roll the dice; see the fear in my enemies' eyes... listen as the crowd would sing, 'now the old king is dead, Long Live the King.'.."
I haven't taken a position.
However, YOU have.
Now, support your position that, while ther may be any mumber of reasons why these people do not go after their targets when the are guns around the poresence of those guns is not highly likely to be one of them.