When the word got out that Rick Perry might have ordered the execution of an innocent man, his popularity went up. It wasn't that folks thought the guy had done it; they'd heard the news. Perry's ratings went up because they respected his moral stance. Justice, to them, was ensuring that for every crime, there was a punishment. Asking "Wait, have we got the right guy?" only increased the interval between crime & punishment. Get too worried about whether you had found the guilty party and you might not punish anyone at all! To these folks, that would have been unjust.

You're making the very reasonable assumption that people want to punish the guilty. 'Taint so. If someone's been hurt, the first instinct is to lash out. The question "Am I lashing out at the right person?" is often of secondary importance. For the MoH in Vval's story, it hadn't even reached that priority.