There are several points to make here:

1. From my discussions with other Gnutellians, it seems to be quite common for new users of Gnutella to start with searches for all the most extreme, illegal files they can think of. In the vast majority of cases, the novelty of the really nasty stuff quickly wears off.

2. Any type of filter would be very difficult to implement, since a wide variety of keywords are used for child porn, for example.

3. As almost 100% of Gnutella users have at some point downloaded pirated music, videos and software, access to the moral high ground is a very steep and windy path. If you were going to apply filters to child porn or snuff movies you would also need to filter out other illegal material or be accused of double standards.

4. The problem is the demand not the supply. Censorship, whether you're in favour or not, is no longer a viable option. With modern technology, wherever there is demand there will be a supply. Hackers, pornographers and Co. will always , by definition, be ten steps ahead of the authorities as a change in official policy requires:
-A period of study
-The filing of a report
-The approval of a plan of action and budget
-The necessary training
-The purchase of any required equipment
All this before the change can be implemented, by which time the crooks are in another league.

5. For me a truly unrestricted net like Gnutella with no institutional or commercial controls like in all the major portals on the WWW is vital for the Internet. The presence of distesteful material is the perhaps the price we have to pay. The only option is self-censorship and to put democratic pressure (through forums like this one or through client chats) on people who distribute this material.