The ISPs aren't banning sites for kicks. New Zealanders have been arrested for distributing the video.
Plenty of parallels between the two. People are hurt in the filming of both. It's damaging to the survivors. It feeds into the fetishes of those who would watch such a thing (it's a snuff film). In the case of this film I could argue that potential perpetrators could study the film for their own plans.
Should the events be discussed? Absolutely. But I don’t have to watch these things to understand how abhorrent they are.
http://www.legislation.govt.nz/act/public/1993/0094/55.0/DLM...
Admittedly, the Chief Censor only published his decision on tuesday, so everything the ISPs were doing before then, they did on their own.