I backed out of trying justify the death penalty for sex crimes because, "sex crimes" are somewhat hard to define. "Date Rape" could actually be consensual sex that was regretted by one party latter. "Statutory rape" laws do need tweaking.
I can think of scenarios were the death penalty would be appropriate; someone forcefully raping a child for example. If there is overwhelming evidence (lets say the sick f*** made a video of the crime) I see no reason to them alive.
Should Michael Devlin, the guy who kidnapped and molested Sean Hornbeck, and Ben Owensbe, be eating on our dimes. I think not. I could care less if he starved to death.