Iranian President Hassan Rouhani issued a threat to the United States.

The U.S. president took it seriously. So seriously that he employed his favorite forum to respond: Twitter. He fired off an all-cap response that says Iran had better think twice about issuing threats.

Hey, I no longer am surprised by Donald Trump’s Twitter fetish. He’s got it bad, man.

I just long ago grew tired of reading these tweets when he decides to issue policy pronouncements or when he articulates some sort of threat to a foreign adversary.

I don’t have a particular problem with Trump responding to Iran’s bluster. My concern is the forum the president keeps using. He blathers these counter-threats for all the world to hear.

I wonder if it ever occurs to Trump to just pick up the telephone in the Oval Office and phoning some intermediary nation (since we have no diplomatic relations with Iran) and offering a warning to Iran to pipe down with the tough talk.

It’s called back-channel diplomacy.

Donald Trump, though, knows nothing of how these matters ought to be resolved. None of that is a surprise, given the utter absence of any understanding of government in Trump’s background.

He goes with his gut, his instinct, his penchant for showmanship.

Dangerous.