I think for death penalty proponents, it's worth thinking about what exactly life imprisonment entails.
And if you read all the accounts of prison rape, forced 'marriages', and auctions of said 'brides', it's easy to understand why such a sentence would be a fate worse than death. Particularly for those who are not physically gifted by nature.
Well of course most 'civilized' countries don't include rape and severe emotional and physical abuse in the standard punishment they dole out to even the most banal of criminals. Might want to fix that one too.