I totally get the anger. I really do. But to share the perspective of one who has been faced with a similar horrific experience...
My son's father shook him violently, and ultimately fatally, when he was 3 months old. Sure I contemplated homicide. However, I realized that a) I'd probably end up in prison (no webslueths back then so I likely would not have gotten away with it) and b) why stoop to that level? I, unlike my son's father, have a conscience and even though I'm a "hopeful atheist," I also wouldn't want to chance it.
Prison isn't fun. Let them rot in there, I say.