If there's a better argument for a parent to go out and buy an AR-15 than armed cops preventing unarmed civilians, intent on protecting their children, from entering an active shooter zone, I don't really know what is.
America was founded on "well if those in charge won't fix shit, we will", and those cops threatening parents with tazers deserve to have their badge taken away at a minimum, and personally, I think they oughta lose their balls, too. Cowardice at that level, where you're biting at those on your own side, in this sort of situation, deserves the harshest punishment.
God forbid I ever have a kid, and I've no desire to own a gun, but if I did, those Texan "law enforcement officials" would have given me all the motivation I'd need to go buy whatever was necessary to protect my family.