Corrected entry: Tuatha uses a spell to disempower a witch, and the spell requires "a fresh human heart". Tuatha is an evil witch, so why is the same spell in the The Book of Shadows, a book of good magic? A spell requiring a fresh human heart is obviously not good magic, and the only way an evil spell could appear in the book is if the Charmed Ones themselves were evil, which they are not.
Corrected entry: Tuatha says that there is no such thing as a courage potion, and when the girls search the book of shadows they also say that there is no magical way of giving confidence. But in episode 1-11, 'Feats of Clay', Piper casts a confidence spell on Doug so he will stop breaking everything in the restaurant.