It’s been a strange few days on the Donald Trump front: He said something about himself that I actually believe and something about the economy that’s mostly true. On the personal side, Trump has been sounding a lot like Adolf Hitler lately — I don’t mean his general tone, I mean his specific statement last week at a New Hampshire rally that immigrants are “poisoning the blood of our country,” echoing what Hitler wrote in “Mein Kampf” almost word for word. (And if you think it was just a one-off, he said the same thing in a September interview.) But...