- You can't take it back if you were wrong
- It's too humane for monsters, when we have things like life without parole in solitary
However, if the debate is about a "humane" way to execute someone, why not inject them with the same drugs we use to knock someone out for surgery? No one debates the effectiveness of these drugs, they work, virtually every-time, hundreds of times a day for millions of people. The only bad side-effects are nausea and death, which aren't a problem in the execution process since the person isn't going to wake up anyway. Once they are out, you can dispose of them any way you like as they won't feel it.