There's less opinion involved here than you make out.
When you kill someone they're dead, period.
You are killing innocent people.
It's not helping anybody or anything.
Reactionaries often want to make you think things are a matter of opinion when they're not. Don't be fooled. A civil society that respects human rights will evolve to a point where the death penalty is seen for what it is, a brutal and ineffectual means of dealing with crime.
In that way it's no different than freedom for slaves, a woman's right to vote, etc.