[Dr. Sivana]

His Holiness was quoted as saying that the thief on the cross, being accepted by Jesus, is an argument against the death penalty

Also, the Good Thief said he DESERVED his fate, and is NOT contradicted by Truth Himself. (Luke 23:40-41, Douay-Rheims)

40 But the other answering, rebuked him, saying: Neither dost thou fear God, seeing thou art condemned under the same condemnation?
41 And we indeed justly, for we receive the due reward of our deeds; but this man hath done no evil.

[xoxox]

And even though He had done no evil, His death penalty was necessary for the salvation of mankind.

Not likely to be a popular argument, but irrefutably true, it seems to me.