a) Being told I can't watch it by the police is pathetic and erodes the respect I have for the boys n girls in blue. The crime is the murder, not the insensitive sharing of a video of the murder.
b) I will not watch a video of someone being tortured/killed. For me, it's a respect thing. By watching it, I'm collaborating in the dehumanisation of the victim and fulfilling the murderers' wishes. If that's hard to get your head round, say it's a video of someone you know being raped. How could you watch that? How could you share it?
Imho, the only valid/moral reason to submit to watching this grotesque stuff is if you're in the business of taking names and doling out smackdown justice.