While I agree with your larger point, that retribution (and worse) is not justice, I wouldn't put too much weight on the study you mention.
It's extraordinarily difficult to 'give details' in a completely neutral frame. Without knowing the details of the study, its hard to say more. It seems likely to me that they probably found what they were looking for.
Given the complexity of legal issues, you can explain away every legal study ever the way you just have.
The point that the study was making is that the vociferous folks frothing from the tabloids aren't operating from an informed position, so their opinion shouldn't be held as the canonical one to base policy on.
My favourite example is this: Politicians love to say "it's the will of the people" on topics like this. "Hey, you industry professionals might not like it, but it's what the uninformed general public want". Strangely, they never seem to take the same attitude when it comes to their own pay packets - all of a sudden it becomes "what the public doesn't understand"...
It's extraordinarily difficult to 'give details' in a completely neutral frame. Without knowing the details of the study, its hard to say more. It seems likely to me that they probably found what they were looking for.