This is total Bulls**t
In every state, the Plaintiff Lawyer Lobby (Those who sue you for damages) will instantly file a suit against anyone who shoots another—regardless of how justified that shooting is.
We who are prudent already have this coverage
What is it the Swiss told the German Nazi's when the Krauts told the Swiss they had an army twice the population of Switzerland. It went something like then we'll have to shoot twice. That was the end of the Nazi's designs on Switzerland.