OK, maybe reasoned debate is lost on you.
The pilot already has a job.
Giving the pilot ANOTHER job, one that requires him to pursue a high level of competence in a completely different field of endeavour, is not a good idea.
Instead, have a third person in the cockpit, one whose task, in the event of an attempted hijacking, is to keep the cockpit secure while the pilot gets the airplane on the ground. This lets people do what they're good at, and concentrate on that to the exclusion of other tasks.
I have read far too many accounts of gunfire getting unleashed at a range of two feet AND MISSING COMPLETELY to be optimistic about the pilots holding the cockpit by themselves without a lot of training--and I hear complaints about "too much training, not enough time for it" from airline pilots as it is.
Reasoned debate is often lost on me these days. I'm not always thinking with my head. I am often thinking with my maternal instincts and a whole host of brand new, often irrational fears.
I don't think, however, that I'm wrong in this case. If we were looking at daily, nonstop, fulltime shootouts in the cockpit we would not be in the air at all anyway. We're looking at the case where having an armed marshall and riled passengers hasn't been enough, and the rare terrorist gets through the newly reinforced cockpit doors (or was maybe in there as copilot to begin with) and there's just ONE MORE CHANCE to save perhaps thousands of people. Most commercial pilots have military training and have above-average reflexes, intelligence, and savvy. They keep cool in crisis and they're trained to respond to a wider variety of problems than most of us can imagine. (How many things can go wrong on an aircraft?) I'll bet that an armed pilot has a pretty damn good chance of saving the situation. He'd have that autopilot on at the first sign of trouble and be ready to roll. I am frankly DISGUSTED by this infernal PESSIMISM that has infected this country. If my kid gets lost in the store, she is instructed to find a WOMAN who LOOKS LIKE SHE WORKS FOR A STORE or a SECURITY GUARD, and NOT TO LEAVE THE STORE WITH ANYONE. These precautions aren't absolute. A woman can be a kidnapper. A security guard can be a molestor. I give her instructions that I think will increase her already pretty-good odds of finding someone she CAN trust. I think that we can trust commercial pilots on the same basis. You're giving them full control of something already proven incredibly deadly--a plane loaded with fuel. What the H*LL is the problem with trusting their judgment with a little ol' handgun???????