"I AM a math teacher at Brockton High School, the site of a school shooting earlier this month. Current school security procedures lock down school populations in the event of armed assault. Some advocate abandoning this practice as it holds everyone in place, allowing a shooter easily to find victims. Some propose overturning laws that made schools gun-free zones even for teachers who may be licensed to securely carry concealed firearms elsewhere. They argue that barring licensed-carry only ensures a defenseless, target-rich environment. But as a progressive, I would sooner lay my child to rest than succumb to the belief that the use of a gun for self-defense is somehow not in itself a gun crime. DOUG VAN GORDER Quincy " http://www.boston.com/bostonglobe/e...ns_teachers_and_self_defense/?s_campaign=8315 Now, tell me again, what was the argument that liberalism isn't a psychosis?