I think parents who let their kids watch a lot of television have become desensitized. My brother's kids probably don't want more than 2 hours of television a week. Without prejudice :-) I can tell you that my two nieces are the most fun, sweet and smart kids I've ever met. Being involved in other activities besides television is the big difference, as far as I can tell.
We were very careful what our kids watched when they were young.
I noticed that my young son reacted negatively to Scooby-Doo...a kid's cartoon....
..he would hide his eyes, and leave the room, and sometimes have nightmares...
..so, no Scooby-Doo for him.
That might sound silly....but the show frightened him.