Discarding free will does not imply individuals shouldn't be held accountable for their actions. No government can provide its citizens an acceptable measure of security from criminal acts if human behavior is unconstrained. However, the justification for individual accountability need not be built on notions of free will or morality. Creating laws and courts and meting out justice are amply justified by the far more pragmatic requirement for constraining behavior contrary to society's best interests.
The fallacy of free will is the ultimate source of unworthy emotional responses such as schadenfreude, the desire for revenge, and superfluous injection of morality into the process of crime and punishment. The latter unnecessarily draws subjectivity, not to mention a good deal of pandering, into a process that should strive to be an objective search for fact and a resolution in the best interests of society at large.
Rejecting free will leads to a more rational approach to crime and punishment by eliciting more appropriate questions. Instead of concentrating on how harshly to punish the convicted criminal, the emphasis should be the more productive question of how to prevent future bad acts by the same criminal or by others.
When the justification for abridging a convicted criminal's liberties is founded on prevention of future bad acts rather than revenge, only the minimal punishment or rehabilitation necessary to achieve that end is justified. For example, life imprisonment is just as effective as administering the death penalty, so it follows that capital punishment is never justified.
But, what about deterrence? Don't the death penalty and other harsh punishments deter crime? The effectiveness of capital punishment as a deterrent is unproven and much pandered, though no doubt fear of punishment in general substantially reduces the number of non-capital crimes. But, once again introducing free will brings an unnecessary complication. Namely, is it moral to execute one person, because it may deter bad acts by others? Panderbear thinks not, even while strongly supporting sure and swift justice for criminal behavior.
The free will paradigm that places emphasis on revenge and punishment as an end in itself has lead America to incarcerate a higher percentage of its population than any other country. We have become a nation of gulags, many of them private enterprises where the incentive is to keep as many people in prison for as long as possible.
By any measure our current criminal justice system is an abject failure. The anachronistic notion of free will contributes mightily to that failure.