Way back in the 1970s a universal policy across all television networks and local stations for all sports was implemented in the US. That policy was to deny streakers (and others) the publicity that they craved when they disrupted a game by jumping onto the playing field (never saw a streaker at a hockey game, funny enough). All things considered, streaking was a minor irritation, but I don't think there's any doubt that the incidence of streaking went down sharply once streakers no longer got to be on the television.
So, what about something similar to publishing/broadcasting manifestos and other publicity-seeking devices provided by mass murderers. Sky News was practically giddy last night when they were able to broadcast the material received by NBC yesterday. I bet NBC was even more excited as the network that actually received the material from the mass murderer. Such honor.
I watched the stuff, but I didn't need to. It was voyeuristic and I didn't feel good about it afterwards. If NBC had simply handed over the material to the FBI I wouldn't have been even a little worse off.
The worst part of it is that you just know there are other psychos out there who will see this as a standard to achieve and overcome. These nuts seems to crave their after-death publicity, so why don't we not provide it? Okay, the first nut to be denied will never know he was denied his publicity, but all others after him will soon learn that fame will not follow infamous acts. It might just help disincentivize mass murder.