You don’t joke about threatening to kill someone. Especially if you are the President of the United States.
Do you just forget that we were in combat with them already?? And it wasn't a joke. It was a threat he made to get them to comply with our demands, which is hardly uncommon.
I can't believe anyone would get their panties in a twist over threats made against "Death to the Great Satan/Burn in the Lake of Fire" Iran, which has been steadily killing Americans for decades now.