It's funny, because I'm actually anti-death penalty, find a lot of what Jason does to be distasteful and ultimately damaging, and think the character himself is completely nuts, but at the same time, I love him so very much as a character, find him incredibly sympathetic, and certainly don't think he's evil, or even a bad person- just confused and misguided.
Actually, I don't think it's funny, I think it makes perfect sense.
If you are anti-death penalty, chances are you are empathic person who believes that people aren't inherently evil and can be redeemed. So it makes perfect sense for you to be sympathetic to a character who has been going through hell since he was a child (heck, if the child rape implications in BftC are real, that would mean that, in his whole life, Jason was only allowed a break in the couple of years he lived with Bruce, and even then he spent every night dealing with criminals and victims).
If anything, I find it really weird that people who are against death penalty are so judgmental and hateful to Jason. What, rapists and killers and torturers of innocents are "still human beings! Killing them is wrong!", but the guy who kills said rapists and killers and torturers of innocents is "sick and evil! Let's vote to get him killed!"? Double standard much?