They made the choice while crossing the threshold or beginning an attempt to break in. I think some people overestimate the amount of guilt they would feel for taking a life in legal self defense inside their home. Though it wouldn't be easy, if they choose to terrorize my family by breaking in, I will shoot.

Outside of the home is a different matter where quick decisions must be made about the actual level of force made against you. In the home no way do they belong there.