I somewhat share in Davys view in the eye for an eye principle. Either the guy that did that to your uncle got too little discipline as a kid, or was abused severely. The point is, if you slap someone in the face because you think it's funny and then get slapped back, a normal person would say "Wow, that hurt! Is that what I did too that guy? That was pretty mean." But some people don't make that connection unfortunately.
It's f*cked up enough to not just rob a house, but to stab one of the people he was taking hostage out of spite means that guy is way beyond help. While I would like to see a person like that stabbed, sewn back up, given time to heal up, and then stabbed again, but it probably wouldn't matter. That person has screwed up his life so much, that there is no hope for him getting better. I'd say put him in the death chamber, but then again I'm from Texas.