Did NBC have a right to broadcast the video? If they show it, it offends the victims and glorifies the killers.
That is the wrong frame to approach the issue. The question should be: do I have a right to see the video? And the answer, of course, is yes. I do have the right to see the killer's psychopathic rantings. And, if I act violently based on that, I should have been identified before. I should have been given a psychological screening before I was sold a gun.
What does freedom mean if it does not include egregious behavior? That is how freedom dies.