Why are people so concerned about the rights of people on death row?

In florida and california they are puting off all executions for the time being because they might be cruel and unusual punishments. But when these people who are on death row were stabbing, shooting, raping, molesting, and torturing their victims, no one dares say that that is cruel and unusual. Regardless of whether lethal injection is unconstitutional, these people still committed horrible crimes and ought to pay the price!