No reasonable person likes violence but we all have a responsibility to protect ourselves, our loved ones and our fellow citizens. Guns are not the only way to protect but they are an effective way to end a real threat in the hands of a trained and competent person.
I have seen nothing saying all teachers should be required to be armed. On the other hand, it is currently against the law for teachers competent in the use and legal requirements of using a firearm for deadly force to carry on school grounds in most U.S. jurisdictions. We are denying their right to self protection and to their fiduciary right to protect other innocent people.
Competent teachers who want to carry at schools do not want to demand any other teacher to carry. However, too many teachers and other opinionated people who do not want to carry, feel that they have the right to prevent others from carrying, even if there are built in safe guards for proper licensing.
Teachers carrying firearms is not the whole answer. Other issues also need to be addressed. But radical hysteria offers no solution. It just encourages sick people to attack the helpless.