Preemptive justice

I know, this is Jackson's blog, and so far I've been a perfect angel about staying on topic. Today, I need to rant. On my drive this morning, I was introduced to a chilling phrase "Pre-emptive Justice". Apparently, its been batted around for a while, and somehow I've managed to miss it. I heard it this morning used in a book review NPR : How Great a Threat Were the Lackawanna Six?. In this case, it refers to the arrest of persons who are linked (frequently using the loose tools of the 6 degrees of Kevin Bacon) to terrorism/terrorists. I'm sure that while the phrase is associated with jihadist terrorism in today's political climate, it could just as easily be used for anyone who can be villainized to conjur up fear.
Justice by definition is supposed to be the great equalizer, balancing the scales between crime and punishment. So, by definition, the only way to preempt justice would require a crime to be committed later on so that "justice" could be served, right?
Personally, I'm not a big believer in the concept of justice as practiced by society. I'm more a forgive'n forgetter when it comes to petty offenses. I don't think you can ever really make up for severe wrong doing. I think punishments are much more useful as deterrents. I believe that what is done in the name of justice is more vengeance than anything. Trying to pre-empt vengeance amounts to a witch hunt. (I wanted another word there, but it turns out there's not one. The closest thing seemed to be "inquisition", and while the Spaniards added a measured negative connotation, its still a legitimate way to say questioning, so witch hunt it is.)