Interesting rant, I dont condone kiddie porn in any way shape or form, but it is just another form of illegal activitiy that Limewire can be used for.

You cant out build criminal activity in your products, apart from it being impossible, criminals are very clever, and would be resourceful enough to find way around any block you tried to put in, whilst the ability of those using the system legally would have been reduced.

IS GM or Ford responsible when someone uses their product as a get away car for a bank robery?

Limewire do a reasonable job, they have a function where flagged adult content can be blocked for the prudes amongst us, and then a key word filter system to further block unwanted content.

MY key word system has words like
underage
lolita
preteen
pedo
baby
kiddy
son
daughter
school
incest
child
year old
"1 yo" through to "17 yo" (The age of consent is 18 where I am)
dad
father
mother

bung these into your key words and you rarely see any underage porn. Yes some people miss name files deliberately, but if you use blitzi, that filters out most of them. If you dont touch any files not recognised by Blitzi you will pretty well eliminate the problem (even if you are stopping yourself from getting any newer content)

have a nice day!