David Letterman was completely out of line yesterday, treating Justin Bieber unfairly when he appeared on his show. Justin got a new tattoo and Dave grabbed his arm, causing the Biebs to scream out in pain. David then instructed Justin to stop getting tattoos. “Don’t go nuts [with the tattoos] … because more and more you see like the mural … like the Sistine Chapel, it’s too much,” the host said to which Jusin replied “I’m not going for the Sixteenth Chapel.” Letterman started laughing before saying “Canadian high school.”