https://www.facebook.com/yudkowsky/posts/10154650743819228?pnref=story
If I were to try summarize very briefly why Trump's remarks on NATO crossed a HOLY SHIT line, it'd be along the lines of: "If you read the history books, you realize that it is REALLY REALLY bad to have any ambiguity about which minor powers the major powers will defend; that is how World War I *and* World War II both started."
And: "In the wake of the second World War that started from that kind of ambiguity, the senior leaders in both the East and the West, enemies though they may have been, decided to learn the lesson and henceforth be more clear about which countries they'd defend. Not only did Trump blow through that, he did so in a way that indicates he has no idea of how World War I started and why this is one of the things you absolutely don't do. He doesn't listen to advisors. He doesn't have advisors! God knows what other guardrails he's going to blow through!"