[luckylion]

> the way we treat bad behaviour should change - people who behave badly should simply be retrained

Does this hinge on us knowing/believing that free will doesn't exist? I'd say it's mostly that we cannot "simply retrain" somebody. If we had an injection that we could give people who's violence threshold is too low, we'd give it to them. But we don't, not even close. That's what stops us, not our belief in free will.