...... in the hope that the rest of us civil beings can live normal, happy lives without them.
Firstly there is nothing civil about killing other humans as a punishment.
Secondly - what if a person confesses to a crime they did not commit and is executed? People sharing your position a gravely unaware of the danger they are in having the guilty walking free. This is just one of many examples that once you go beyond the the point of no return you introduce greater risks and unknowns.
How about instead of killing these broken people we study them and see if we can learn more about what caused the issues in the first place.....I dunno - maybe we could look to *fix* problems rather than kill off symptoms...?