Some of you guys may remember the Manson family and the Tate-LaBianca killings. Although I'm not old enough, I have read a bit about it. So if a stranger enters my house and does not obey my instructions to leave, or makes ANY threatening comments, gestures, motions, etc to cause me to believe that I or any occupants of my house may be in any harm, I'm going to do whatever I feel is necessary to protect myself and the other occupants of the house from the stranger. If he's clearly unarmed, it might just be a punch to the nose......but if I can't tell with any degree of certainty if he's unarmed, or if the gun is real, or loaded, I'm going to assume the intruder has the worst intentions and I'll act appropriately to protect myself and any other innocent occupants in the house. So if I have a gun, and the intruder has a gun, one of us will likely die.
Argue all the legal/ethical issues you want, but if some scuzzbag breaks into my house, he's already shown a disregard for laws and ethics, & I'm not going to wait & see how far he's willing to go with his crime-spree, I'm not going to flinch if threatened, I will give HIM a chance retreat, but otherwise, one of us will likely die.
Call me trigger-happy, or bloodthirsty, or whatever. Just don't break into my house & threaten the occupants.