A survivor of Auschwitz is asked what is the most important lesson he has learned in the last few years. He says, “When someone says he wants to kill you, believe him.”The earliest source I Google for this quote is Newt Gingrich, testifying before a U.S. Senate committee in the autumn of 2005. Newt was alluding to threats against Israel made by Iran's Ahmadinejad, and the seriousness with which they should be taken.
Perhaps the quote should read "when an Austrian demagogue says he wants to kill you, believe him." When the speaker is an Islamic leader in the Middle East, he may or may not be serious.
Most Iranians who shout "death to America, death to the Great Satan" do little to make that happen. Similarly in Iraq, Sadam's "mother of all battles" turned out to be the mother of all routs. In Arabic and Persian there is a linguistic convention of florid overstatement that should not be confused with, and is often a lame substitute for, planned action.
