re: Your answer explains
The advice that Jesus gave to Peter
"Neither cast ye your pearls before swine"
But it does not cover the question of: If you kill a killer then do you not invite to be killed?
Suppose that some stranger murdered someone in your family and you went and murdered that person, then (according to the “Do unto others as you would have others do unto you.†[Matthew 7:120] ) you should be murdered also, but then if someone does murder you then they also should be murdered.
It seems to me that such a loop of murders will never end.
What is your viewpoint of such a thought?