The amount of evidence required to convince the average TV-hypnotized American is almost zero. However, in the rare historical moments where actual independent journalists and politicians exist, a modicum of evidence is required. From the invention of the Gutenburg Press onward, the boldest of lies could be made palatable by dressing them up with a few witness statements and anecdotes. Actual evidence was never required; even court proceedings could be invented out of whole cloth, using phantom "special prosecutors" and other imaginary personages.
The Israeli-Palestinian conflict, having been staged from the very start, never required any evidence. Israel was designed as a series of closed set compounds, with timid soldier-settlers crouched in fear within and special forces setting off explosives without. The journalists simply documented the play-by-play. The Palestinians were happy to play along, with the prize being a visa out of that hell hole. The Israeli project has amassed huge fortunes for the top families, and they are using seasonal Intifadas to keep real estate prices low as they transform the area into their world headquarters.
Other staged dramas, from the Moon Landings and the JFK assassination to Waco and 911, required more evidence due to the open nature of society and changing media technology. With so much ham-handed fakery accompanying the World Wars (the most obvious being created by the Soviets) media consumers became more skeptical. Western media responded by screening newsreels and by fielding action reporters "on the scene". Autopsy photos and other manufactured evidence began to "leak" into the hands of "independent" journalists. Conspiracy theories and conflicting narratives were inserted into the earliest scenes in order to contain and direct civil discourse. Political groups formed overnight in order to paper over plot holes or further distract an increasingly suspicious public mind as the economic noose began to tighten.
In the Post-Sandy-Hook World, hamhanded fakery is again very much in evidence. This time they are relying on rapidly-improving video editing software, the rapidly-eroding public attention span and the 24-hour newscycle to keep Western audiences feeling threatened. The sky is not the limit these days, and there is much more to come. Once computer graphics become indistinguishable from reality there will be no more crisis actors required. There will be no more accidental admissions during interviews, no more video glitches to analyze. At some point in the very near future pre-determined plot lines will be inserted into live streamed recordings without any risk of detection. At that point we will have to rely on our common sense and our knowledge of fakery throughout history in order to keep our feet flat on the ground.
On a more positive note, the fact that Youtube is censoring channels is a sign that the mass media has lost control of us. As Hillary lamented, "We are in an Information War, and we are losing that war."