My impression is that very few on the U.S. left have any support for the death penalty. This dovetails with their absolutism on abortion and their general isolation from the working class.
To say it is "popular" is not quite apt. Like saying root canal is popular. It is seen as justified, if regrettable (for all the reasons raised).
There may be some erudite rap about moralism but when I see people trying to do what they think is right, instead of what they know is wrong, to me that reflects a positive, humane impulse, even if I disagree totally with the other's notion of 'right' (though there are exceptions to everything). I don't lay claim to any superb morals myself. I can recognize when people exceed the speed limit, even if I do so myself. I can stipulate what a moral course is, without preaching and urging it upon everyone, and be right, even if I am not up to following it myself. I don't think we're here to assess each other's character, but to sling ideas.
I don't see the individualism angle as essential. Retribution often has a group aspect to it, no less than an individual one.
The hedonism reference is completely baffling.
Nobody has responded to my query about why working people are more supportive of capital punishment than those w/higher income.
mbs