Tim Kaine is citing his religion in defense of his opposition to the death penalty. His new ad (last one here) has him saying, "As a Christian missionary in Honduras, I learned that life is sacred. And that's why I oppose the death penalty. I'll carry out a death sentence, because that's the law, but I won't change my religious beliefs."
A few points:
-No one's questioning his religious belief. They're questioning his activism against the death penalty. Likening it to the gulags shows a callousness for the most grave injustices.
-He only learned about the sacredness of life in his 20s? He was raised Catholic, so why didn't that sink in before then?