I have offered solutions to the filter arguements. They are common sense approaches. Provide several computers that are not filtered. Children must have an adult to use those few computers in a library. There's your adult supervision. The other computers are filtered, for those children who have parents that don't care or cannot find the time to always be with their children.
The library should be a safe place to leave a child to be. The library visit should not be a porn store.
The wonderful comments from others about filters not working correctly is so amazingly idiotic it is hilarious. No, it is not foolproof, especially if you spend $45 at walmart to buy it. A good filter placed at the DNS server can easily and effectively filter without causing nazi censorship or blocking "little girl" searches which would yield no results on a cheap filter. The filter arguement is a mute point, because it is made by those with limited computer technology experience. A library can be effectively filtered. Simple common sense accomodations can be arranged for unfiltered access.