"I think its fair to  say most rational people would agree that weapons don’t belong in a university classroom"

No, it isn't fair to say that. Many many rational people disagree.  Those with concealed handgun permits have their guns at a variety of locations.  When you make something a "gun free zone" the only one obeying that law are the lawful.

You wouldn't think a recruiting station is a place where a handgun is needed. But because a Marine violated military rules, other marines are alive and the terrorist is dead.

There is no "rational" reason to restrict those that are concealed handgun permit holders from bringing their firearm on campus. There are numerous reason that people bring up.  But when you take into consideration how many people have been killed in "gun free zones" and college campuses, that other group of "rational" people, find these reasons to block permit holders irrational.