I acknowledge that I'm pretty slow, but it sorta crept into my meager knowledge base somewhere along the line during the years I spent acquiring a PhD in psych and then teaching statistics and doing research and program evaluation studies.

You're certainly right about the race & class bias, of course.

I would suggest as an alternative hypothesis here that maybe those states with the most brutal cultures have both the highest murder rates and the highest execution rates because--surprise!!--they are brutal cultures ruled over by demagogic, fear-mongering and racist politicians. One of the first steps that might help in reforming a place like that might be to eliminate the death penalty. People are going to be no less safe with a policy of life without parole than they would be with the death penalty.