Earlier quoted context omitted.
It was not the justification of murder I was talking about. Simply the fact that murder as a solution is absolutely accepted in the US.
Murder isn't the same as homicide. By definition the death penalty isn't murder, because it's state sanctioned. Self defense, another example of legal killing, also isn't murder and most people who are against murder would consider a death in self defense to be justified and not murder.
For example, we can go into treacherous schemes that pushes our neighbors into paths where the only obvious option they can still perceive as a way to escape our shenanigans is an attempt to kill us, and as they come with this very real intention to kill us, press the button we had prepared to trigger some mortal trap.