Lessig isn't saying we should keep children away from morals. He's criticizing how Disney adapted the Brothers Grimm's stories, which often preached heavy-handed and regressive moral lessons in a moralizing manner.
What lessig is likely referring to is the violent and grotesque consequences of the original Grimm stories as well as their brazen antisemitism.
https://www.history.com/news/the-dark-side-of-the-grimm-fair...