I really like I2P as a project, and I think it gets a lot of things right. For example having every network participant relay some internal traffic, instead of relying on altruism from relay operators, makes it much harder for a single entity to control enough hops to deanonymize users. Sadly, outside of torrenting I2P doesn't seem to have much traction, losing out to the better funded tor project
One of the reasons people were wary of Freenet, where every user would participate in the hosting, was that if the encryption algorithm was ever broken, people would undoubtedly be revealed to have been passing CSAM along. Unwittingly, but still. Does I2P’s model not spark the same concerns?
I am pretty sure not blaming the messenger for the message is a legal notion that predates Hammurabi's code.