I don't think training with and carrying a firearm is "armchair commando" territory. The site is ETS; different equipment is needed for surviving different situations. Certainly I don't advocate "going Rambo" or inserting yourself willie-nilly into situations you don't understand. But the fact remains that in an active shooter situation you're likely to be your own first responder. Your response could be to freeze, to run, to shoot back, etc. Having a firearm on you doesn't require you to use it but if you're unarmed several options are removed from the table.

In some active shooter situations the only goal of the shooter is to kill as many people as possible. It's hard to imagine how you could make that situation worse by resisting short of actually shooting innocents yourself. It should go without saying that you're responsible for ever bullet in your gun.

Ultimately it's a personal choice to CCW or not to. Some problems can be solved with a firearm, others can not. Resistance carries risk as does meek compliance. The risk is never zero.