Children shouldn't be secluded from the unglamorous parts of society because with the knowledge of evil comes the possibility to turn it towards good! Just like Prince Gautama, who's Father withheld from him the dangers of society and the knowledge of poverty, hunger, and death, yet on his own he set out and discovered these things in the world, he is known the world over as the Buddha, for the great works he did in response to the ailing world around him.

Now, as I'm not a parent, nor ever intend to be, I can only ever speculate how to raise children, and while my sentiments above seem idealistic, it is also unrealistic to pretend that your bettering your child by removing from their path all matter of controversal materials. Parents shouldn't be so over-protective of their children and blame libraries for carrying the controversial materials. It is not the job of the library to influence people toward a point of view or to convert them toward your way of thinking. The job of the library is to reflect society in general, to argue both sides of the story, and to represent all manner of peoples. If an item is upsetting to you because of obscenity, or other reason, point out to your child why you think it's wrong and how they should act accordinly. The solution isn't always to yank a book/video/magazine from the shelves.