I used to read while watching television, so I don't see the problem with letting a kid watch TV. I'm of the opinion that "TV rots the mind" is too general a statement to be useful. There are shitty television programs/movies, and there are really artful, educational, and engaging TV shows/movies. If you're plopping them down in front of Jersey Shore, you're a terrible parent. If it's The Princess Bride, Labyrinth, or Cosmos, you're the best parent ever.
eta: if we're talking about a baby, TV probably isn't engaging enough. I'm thinking of older children, toddler and older.