Nick Shapiro — a former CIA deputy chief of staff in the Obama administration, who helped orchestrate the letters — tells me that a major concern of many of the signatories was President Trump’s implicit threat to current intelligence officers:

“It’s setting up a system where the national security and intelligence apparatus is being told: ‘You better just agree with the president, and you can’t give him news he doesn’t like.'”

“That’s a very dangerous thing: It’s the exact opposite of the climate and culture you want in your intelligence team.”