My simple answer is, yes.
For the simple fact that a life spent staring at screens is not a fulfilling one, is not a happy one, is not a healthy one, is not a rewarding one or a useful one. Children should be outside, playing with their friends, playing with their parents, learning to play by themselves, getting their clothes dirty, climbing trees, making potions with mud and bits of the garden, having secret conversations with fairies and sprites, using their imaginations, pretending to be knights or elves or spacemen or superheroes or tiny little two-inch lost people fighting their way through the tall grass.
Modern technology curbs the imagination, and leaches the childhood out of children. They only get one chance to make their youth a good one - we shouldn't rob them of it by sticking them in front of screens every time they get a bit energetic and enthusiastic.
Everything in moderation, technology included. My own children watch television, and play the occasional video game, listen to their iPods and occasionally dip into their vast collection of DVDs. But these things are used as a last resort when bad weather prevents them from being outside, and when we really can't think of anything else to do because every toy has been played with a million times, and the poster paint has run out, and there aren't enough ingredients for baking cakes, and everyone's too tired for a game of hide-and-seek, and no one fancies a tickle fight, and eyes are too tired for reading.
Yes, I believe that parents have a serious moral responsibility to ensure that their children are not exposed to an adult world too soon. I haven't answered your question properly, because I've gone off on a tangent about playing. But it amounts to the same - they should be busy being children, not learning about being boring, one-track-minded adults.