Retribution is explicitly used as a justification for legal punishments like the death penalty. I could get out Nietzsche's Genealogy of Morals and make an argument against it, I suppose, but nonetheless it's taught as such at law schools throughout the country.
Not sure I buy the "respect for the law" argument. If I understand right, you're saying, basically, "the death penalty is on the books, so if it's not used, then the law won't be respected".
I'd turn that argument on its head and say that in practice it's currently used too frequently but not respected. There's something over 3000 people on death row, and it takes years to carry out an execution.
The result is a situation in which criminals probably don't feel any additional deterrent from the death penalty and no one has much respect for society's abilities to enforce its laws.
Hence, you'd get a lot more bang for your buck by 1) drastically reducing the scope of the death penalty punishment to the smallest number of the most horrific criminals and 2) employing the penalty fairly quickly in those cases. Like, commute those 3000+ people on death row down to life imprisonment, but then go out and execute Charlie Manson, Dick Cheney and Barney Frank quickly and publicly.