While some people need killin' for sure, our government can fuck up a gas can. I think it's a legitimate argument from a conservative/libertarian point of view that they abuse and misuse any power we give them, and they demonstrate time after time that they cannot use the power they already have in a responsible way.
Even the judiciary is totally politicized and captured by the left. As we see with political prosecutions and gross miscarriages of justice and "judges" who don't care what the law says as long as they get the outcomes they want, it is entirely reasonable to question if our judicial branch is capable of dispensing "justice" when they selectively prosecute, and judges disregard the written law.
It doesn't come from the left at all when I ask: Is our justice system good enough to make an irreversible decision? There are plenty of cases where I think the perpetrator is guilty as hell and deserves to be kicked off the planet, but that doesn't mean that I trust our government enough to give it the power to kill it's citizens. Don't assume that because someone is against the death penalty it means they sympathize with criminals. For me teh conundrum is how aweful I think our government is, and how poorly our judiciary is staffed. There are idiot judges on our supreme court. How many idiots populate the rest of the judiciary? How many are purely political animals who follow their sick politics and not the law? More and more I see rulings that are literally out of left field. Doesn't inspire much confidence in a blind justice capable of making an irreversible decision.