how is the user going know the brokenness you net vigilantes propose to impose from the brokenness the other miscreants impose? Nicely put. How about: if their mail and web access works, then its the fault of the net vigilantes and filtered Internet service. If their machine is running 100% on the CPU and rebooting at random after just a few minutes online, then it's those other miscreants...
as an exercise, try to write the end-user-level document on how a typical end user can tell if application X, for a very large range of X, is not working because of an isp-imposed firewall or filter, miscreantware, or the application is actually broken. if you can't write this, i suggest you have real problems justifying firewalling/filtering without the users' *informed* consent. think about "i am suing because you just cost me three days of lost revenue, six people's work, ... because my critical application was broken by your ...". i am sure keith moore will be glad to help you with such a document:-). randy