I haven't read anybody calling for the Presidents head, nor has any one suggested that the pilot should leave the cockpit to assault a gang of terrorists in the aircarft passenger cabin. THINKING people, who have some experience in the world, realize that any door may be broken into. If the terrorist does get through the door, which he probably can, eventually, if the pilots are unarmed, you have given the terrorist a potent weapon such as the 9/11 aircraft. The terrorist will be armed. That is a certainty. Should not the pilots at least have a chance to defend the cockpit?
Or sneaked through, unless the airlines install dedicated pilot lavatories.