They were discussing morality, not legality. There is a difference. You can base your decision to do/not do something because (you feel) it is immoral, whether it is illegal or not.
Often legality and morality do align (but really not as often as you'd think), and this is fortunate, because it allows good people an easy mental short-cut for weighing one's actions based on legality (and punishment), as well as protecting the weaker-willed parts of society that often end up on the wrong end of moral decisions by people like sneak, who'd let people drink themselves to death because if everybody was completely free they'd surely decide out of their own free will to do what's best for them and nobody would ever prey on the weak-willed like that, ever.
Often legality and morality do align (but really not as often as you'd think), and this is fortunate, because it allows good people an easy mental short-cut for weighing one's actions based on legality (and punishment), as well as protecting the weaker-willed parts of society that often end up on the wrong end of moral decisions by people like sneak, who'd let people drink themselves to death because if everybody was completely free they'd surely decide out of their own free will to do what's best for them and nobody would ever prey on the weak-willed like that, ever.