I don't really understand the people who are upset with John for writing a story with a particular angle, in this case against the death penalty. How else should he convey what his character feels about an issue. If you don't subscribe to those same views, then just enjoy the story for what it is, a great legal thriller. And if you consistently find yourself repulsed by his stories, well then stop reading them.
For the record, I am a conservative and I happen to be pro death penalty, and John Grisham is one of my favorite authors.