Author Michael Bender Says Trump Threatened Him Over Alleged Hitler Convo

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 was gracious with his time, Michael says there was also threatening language involved.

As we reported ... Bender's book claims Trump was visiting Europe in 2018, commemorating the 100th anniversary of the end of WWI, when at some point during the trip Trump turned to his then-Chief of Staff, Gen. John F. Kelly and allegedly said, "Well, Hitler did a lot of good things." Kelly allegedly pushed back.

Bender claims Trump's response to the alleged Hitler conversation was to call it defamatory during their face-to-face meeting ... which he took as signaling a potential lawsuit if it ended up in the book.

Of course, he did include it ... and told us why he was supremely confident, despite the threat.