If a criminal was kicking down my door with a gun, I would shoot him for self defense for myself and my family.And if it was a criminal kicking down your door with a gun to kill your family including your children and you didn't have a gun?
I might respectfully point out that the homicide rate in Australia stayed relatively constant even after strict gun laws were implemented.
Ringing a doorbell rarely precedes an armed killer breaking in. If the home owner is that paranoid to chase after and shoot a door bell ringer, then he has mental problems and should not be around firearms.
I'm not against guns, many responsible law abiding Americans own them. I'm against angry gun nutters who use them whenever they're triggered or disagree with someone.