The book is not exactly like that. This is much more a 'world-gone-wrong' with Alex being the oldest of his Drugies at 15, the rapes are of 10-year old virgins and the whole scene is much uglier than the rock&roll approach in the film. Naturally he couldnt use especially young people in the roles.
I somewhat disagree, from the film I really get the impression that it is also a world-gone-wrong with gangs that lack empathy, but you're right about the age difference. Two movies with violence and children that I have always thought were very close to the theme in A Clockwork Orange and that actually do use children are Kids and Bully. I appreciate your opinion on the book and movie.
I don't think that people watch this movie and go out and commit crimes because of it. I think already disaffected young people get their ideas from movies, TV, the Media, and anything influential and then you read about them in the news. The appeal of Natural Born Killers was enough to influence a young couple to shoot random victims along an Oklahoma highway in 1995. I think anymore if a young man beats up a homeless person it's not necessarily because of ACO anymore, because they see it on the news, on Youtube.
But aside from that, it has always been 'cool' to be into these violent movies. The Godfather, Scarface, just think of a movie you're not ashamed to be really into and most likely it has some ultraviolence in it. My guess is that the violence is a form of protection from the various evils of the world, and that if you can commit it, you are in essense surviving by protecting yourself from the forces that threaten to destroy you. We live in a society that frowns upon violence except as a last resort for defense, so we need to see it in these movies, to feel that rush that only violence can bring. And at the same time, were we to actually commit it, we then have to struggle with our own consience afterward. This is just a guess, as I haven't committed violence or ever killed anyone, but my guess is that whether or not you intend it, you will have to consciously struggle after it's happened.