Retired four-star Gen. Barry McCaffrey doesn't tweet often, but this got Lawrence O'Donnell's attention on his show last night.

Unfortunately, the phone discussion was cut short by breaking news about the firing of Andrew McCabe, but it's still worth noting.

Rachel Maddow told O'Donnell, "I'm glad you're having him on. I would love to hear why he came to a conclusion that serious."

"We remember the press conference, 'You must never doubt the generals." And now joining us by phone is General Barry McCaffrey, a retired four-star general and an MSNBC military analyst," he said.

"Thank you for joining us tonight. And I'm wondering why tonight what was it that brought you to the point of seeing this president as a threat to U.S. national security? I know you didn't choose those words lightly."

"No, not at all," he agreed. "I've been critical of the president for a variety of reasons, but the turning point in my mind was the reluctance to stand with the Brits over what has been a documented series of essentially Russian intelligence murders in London. And the latest one being really a signature attempted assassination of the former Russian intelligence officer and his daughter using a chemical agent that was clearly only available to former Soviet operatives."

That's when he was cut off, but I have a feeling he'll be back soon.