Part of the didactic value of fairy tales lies in their ability to clearly depict goodness and evil. This basic moral system is helpful for young children, but it is also useful for older audiences in a society that often blurs these distinctions. A morality based on absolute truth, rather than relativism, teaches the intrinsic goodness and evil of certain actions. Fairy tales show that good actions are rewarded while evil acts are punished.
In the old tales, the hero and/or heroine win. Moreover, the evil characters receive retribution. At the end of Ever After, Danielle and the prince are happily married while her family is subjected to the housekeeping duties they once imposed upon her. Less gruesome than the original Grimm, perhaps, but nevertheless effective.
Several of the versions with which today's audiences are familiar show the prince and princess living "happily ever after," but the wicked characters often go unpunished. Disney's Cinderella concludes with prince and princess living happily ever after, but no mention of what happens to the wicked stepmother and stepsisters.
Good is good; evil is evil.
Traditional stories show heroic princesses, valiant knights, and kind fairy godmothers fighting wicked witches, gruesome ogres, and evil sorcerers. In "Jack and the Beanstalk," a cruel giant who eats little boys has overtaken their former home.
In the spirit of tolerance, modern retellings show "human" heroes, replete with flaws, pitting themselves against antagonists who may be misunderstood simply because they look different. While overtly a parody, the ogres of Shrek suggest that traditionally wicked characters of folk literature have been largely misunderstood and persecuted.
While several factors influence a person's decision to choose to do good or do evil, every choice is an act of the will.
Classic tales show heroes and heroines fighting against all odds, but the choice to do good leads to triumph. George MacDonald's The Princess and Curdie, sequel to The Princess and the Goblin, shows that while Curdie has many opportunities to follow the crowd or permit evil that might not harm himself, his repeated efforts to do good ultimately bring about good for the entire kingdom.
Today, characters' choices are complicated and influenced by many factors. In some cases, heroes take on an "ends justify the means" mentality (cf. CCC 1753), and in other cases, the evil actions of wicked characters is rationalized because of unfortunate circumstances. The evil queen in Snow White and the Huntsman is shown to have suffered much in her own childhood that precipitated her ascent to power, but she misfortune does not justify her present actions.