AASLF thank goodness there are some reasonable responses like your on this thread. I think some of the others are living in a dream world.
Rules, carts, Tasers, and guns and other internal things which I won't discuss may or may not stop terroism. But the terrorists are going to strike next at those places where some of the people are now laughing at efforts put forward to stop or reduce threats. They obviously have not been through was AA and UA have experienced. Maybe their turn is coming and it won't seem like such a joke.
As you say, passengers have killed people who have attempted to get in the cockpit and those who try MAY get killed in the interim with the questions asked later.
You may have followed the UAL 777 case to GRU or EZE where the idiot tried to get into the cockpit during cruise. Unfortunately the crew only used the flat edge of the battle ax on him and got a little blood and the guy is in jail. I personally would have used the blade numerous times, chopped his head off, and written it up in the logbook that the AX needs sharpening and cleaning.
Next issue.......