Does TV really rot your brain?

Why do people say TV rots your brain? What about movies? I personally get so much knowledge and insight out of my TV watching. I think I've expanded my mind by watching shows that have a different perspective than mine on many varieties of subjects.  We can't forget the "educational" channels as well. My family loves to sit down and watch the Science, History, National Geographic, Animal Planet, etc. We have discussions on the things we find interesting or if we have knowledge of our own to add. Check out this post by Frank on the Singularity blog. He has a great response to the myth that TV rots your brain. What do you think?