All of the teachers at Hogwarts were armed.



Teachers like Lupin taught students how to properly defend themselves, while government shills like Umbridge insisted that they need not learn defense against the dark arts because an armed and competent population was a direct threat to government overreach. 

I bet in a moment or two JK Shilling will jump out of nowhere and claim that umbridge actually was there to represent the NRA and that self defense against the dark arts really meant abolishment of weapons.