Original sentence: A frequent argument by debunkers of "conspiracy theories" is that such consparacies would require a lot of people, and that it would be hard to count on so many people keeping quiet.But he says that a number whistle blowers such Kevin Ryan, Sibel Edmonds, and David Schippers have actually come forward in spite of this.Griffin also says that it's possible that people with knowledge may have been threated that their carrears could be ruined or that even physical harm might come to them or their families.In response, members of the 9/11 Truth Movement, such David Ray Griffin, author of The New Pearl Harbor, have argued that many of the people involved would likely not know the full extent of the plot.”    Griffin elaborates that many would likely feel that they have little incentive to talk in spite of such threats, given the lack of interest on the part of the mainstream media thus far
Edited sentence: David Ray Griffin, author of The New Pearl Harbor, a recent book describing many of these theories, believes that members of the FBI, the CIA, and other intelligence agencies have knowledge of facts that conflict with the 911 report, and have been told by government officials to not reveal these things, and threatened that if they do, that their families may be harmed.”  Source:  The Santa Barbara Independent