Former President Donald Trump threatened to sue over the new book detailing his alleged praise for Adolf Hitler … according to the author, Michael Bender, who says he was summoned to Mar-a-Lago for a one-on-one. Bender joined us Tuesday on “TMZ Live” to discuss, “Frankly, We Did Win This Election: The Inside Story of How Trump Lost” — and he told us how Trump tried at first to gently spin the content of his book … before taking a more hardcore approach. The WSJ reporter says Trump twice invited him to Mar-a-Lago after leaving office … and while the ex-Prez...