I don’t disagree with you but I think there is and has been so much publicity of this event that the video (and I don’t think it needed to be shown) is not necessarily what pushed him over the edge. In some ways, if this guy was going to snap, I’d rather he snap now while everyone is watching for it then in a month or a year when the guard is back down. Having said that...who knows what goes on with these whack-jobs. He’s also a meth-head.
I suspect this would've made him really look like the true psycho he is, and remove any doubts about the level of malevolence in him. As NBC did it, one is left guessing what they edited out and why, while the parts the editors wanted us to see are continuously repeated, and the all the hype for the footage has the effect of lionizing the killer as somebody special.
Granted it would have ended up being recorded an readily available all over the place (as the excerpts are now), but the whole thing would have been out there for the record.