Negatives stemming from the free will myth
Retributive attitudes supporting harsh criminal sanctions
If offenders are seen as the ultimate source of their deviance (e.g., addiction) and criminality, then they are deemed deserving of punishment on the grounds that they could have overcome their environmental and biological circumstances, but simply chose not to do so. This sense of strong, ultimate desert is used to justify capital punishment and punitive incarceration over and above that necessary for rehabilitation or deterrence. Such punishment reinforces and perpetuates violence and maladaptive behavior, leaving in its wake vast and unnecessary suffering.
Ineffective social policy
To the extent criminality and harmful deviance are understood to arise from individuals' undetermined choices, their true social and economic causes will go unaddressed. The myth of libertarian freedom essentially lets us off the hook from having to thoroughly investigate and remedy the root causes of dysfunction, and so the cycle of crime and punitive response repeats indefinitely. Free will is the bottom line excuse and justification for laissez faire and ineffective social policies which guarantee high levels of criminality and dysfunction.
Positives stemming from inclusive naturalism
Softening of retributive attitudes
Understanding that people don't create themselves, but instead are fully included in the causal matrix of environmental and biological conditions, undercuts retributive blaming focused on the person. This should help reduce the demand for capital punishment and harsh prison conditions. The aims of criminal justice might shift from the retributive imposition of just deserts to public safety, rehabilitation, victim restoration and reconciliation, and the prevention of recidivism (see note 1 and the Criminal Justice page).
Enlightened social policy
Inclusive naturalism leads to the conclusion that an individual's development and behavior are fully a function of biological and social conditions, in which case the desire for a better, less punitive society should lead us to address these conditions. No longer will the free will myth excuse inaction on the grounds that people willfully choose their criminality, addiction, etc. Moral distinctions will still be made, but moralistic responses will be lessened in favor of interventions (e.g., economic and social investment and reform) which actually alleviate the causes of criminality.
See the proposal for Council on Crime and Causality.
 See Derk Pereboom's book, Living Without Free Will, Ted Honderich's book, How Free Are You?, and Paul Breer's book, The Spontaneous Self, for arguments in favor of policy change in the light of inclusive naturalism, especially in criminal justice. See Honderich's website for brief version of Pereboom's radical thesis on dismantling institutions of punishment. Note, however, that belief in naturalism is no guarantee of softer attitudes on criminal justice, desert, and blame. See, for instance, my review of Michael Moore's book, Placing Blame, in which he defends retributive justice despite his acknowledgement that we don't have libertarian freedom, and my exchange with David Hill on What Justifies Retribution, Precisely?.