Sir David Attenborough was one of the most trusted and admired men in the world - until early 2019, when he narrated a joint Netflix/WWF documentary called Our Planet that showed several walrus falling off a high cliff to their deaths on jagged rocks below. Hundreds were shown to have died, which Attenborough blamed on humanity's wanton use of fossil fuels. Many viewers, including children, were traumatised by the brutal images. He used this...