Charles Schultz has a large vested interest in keeping the integrity of the Peanuts universe; with it he makes books, movies, merchandise, ect.

If I start producing a Peanuts comic and I portray Charlie Brown as a meth head that starts kicking Snoopy and pimping out Lucy, it will degrade the intellectual property that he has built and will cost him in lost revenue from missing ticket sales on movies, lower book sales, ect.

Just because I can easily do this does not make it right (it will cause monetary harm to Mr. Schultz), it also does not negate Peanuts being an intellectual property.