I doubt they are actually worried about what Graham Hancock is going to say. After all his deal is: "there used to be an ancient civilization that had advanced knowledge of astrology and building etc, which was destroyed by a cataclysm at the end of the last ice age/ younger dryas." He suggests that the reason for the cataclysm was a series of comet strikes, a hypothesis that is gaining strength in paleo-archaeological circles. Archaeology also accepts that Gobekli Tepe was buried some 11,500 years ago so why is Graham's ideas which are nearly acceptable common sense seen as such a threat? These attacks suggest he is over the target, but which target? I doubt it is the "Younger Dryas was caused/ended in a world wide cataclysm". I doubt it is the "there used to be civilizations that were more advanced than we thought in prehistory." either. We have too much evidence of reasonably advanced prehistoric civilizations as it is. So what target is he over? I think they are worried that this will lead people to the idea that our sun is a recurring micro-nova and that the disasters that affect this planet are cyclical, occurring every 12 thousand years. That the climate change we are seeing is down to these changes which happen on a galactic level and that we are due the next one in the next 30 years.