"So-called violent criminals"?  What in the world is that?  If you are a convicted criminal, you are not "so called".  
You keep pushing this "crystal ball" analogy but it is not magic. If a person is charged and convicted of violent crime(s), he/she is a risk to society.  I need to be shown proof before I believe some study about their "lowest recidivism rate". 

Because I challenge the District Attorney's poor decision and you disagree, I am now responsible for the perpetrator's murder in your mind swamp.  I will stop hoarding my rice and beans and start serving free lunch on my front lawn in an effort to stop killers from killing.  I hadn't realized the connection until you enlightened me.