I'll have to agree with this comment by "Jason":

   Victor Mair quoting a colleague said:

   "In 1998 when the reformist president, Mohamad Khatami, came to power he tried to eliminate this slogan from the political scene and he suggested to replace any 'marg bar' slogan with 'zendeh baad my opponent'."

   Why would he try to do this if "marg bar X " neutrally means "down with X", not "death to X". Similarly:

   "Alireza is right to try to downplay the slogan — for two reasons: 1) This is an early revolutionary slogan that is quite exaggerated. 2) Not many Iranians actually subscribe to this view…The official government uses this slogan, but not many actually take it seriously."

   Again, why is your colleague /so concerned to downplay the significance of this slogan/ as "exaggerated" (whatever that means — do they mean "hyperbolic") and "not taken seriously" if it merely means "down with America?"

   Frankly this piece reads like pure political drivel of the type that's increasingly infecting Language Log of late, when it seems perfectly obvious that:

   1) Marg bar Amrika literally means "Death to America"
   2) Native Persian speakers are perfectly aware of this fact, or else why try to euphenize/euthemize the expression or downplay how "seriously" Iranians take it?

   Reza Mirsajadi's effort in sophistry reminds me of David Irving's attempts to prove that "ausrotten" doesn't mean "exterminate". And indeed, given what happened to the Shah, the fact that the phrase originated in the Iranian revolution is the opposite of comforting.

   Violent metaphors have a long provenance in all langauges, but in the age of terrorism and the twitter soundbite every English speaker has had to learn to avoid them /precisely because/ you can never know if such threatening language is sincere or not. I fail to see why Iranians should get a free pass and a translational obfuscation courtesy of Mirsajadi on such language. Can anyone trust Mirsajadi to translate honestly after this particular effort?

You may as well claim "go kill yourself" is an idiom that means "I don't like you". An idiom is when it's nearly impossible to infer the actual meaning based off the literal meaning of the words. A hyperbole or a metaphor does not make an idiom. Death is invoked here exactly because of what it implies. "Death to X country" is not any less metaphorical in English. A country obviously cannot die.

Ah, then CNN could do a better job translating. "death to" and "down with" have pretty different meanings.

The problem they face, is it has become a well-known tradition in American (and Western) journalism, going at least back to the hostage crisis in 1979. If they change the translation now, people will attack them as pro-Iran/pro-regime/etc. It is possibly an even bigger problem when it comes to the use of the phrase against Israel; I wouldn’t be surprised if a change of translation in that context got labelled as anti-Israel, anti-Zionist, even antisemitic. The politically safest course is just to keep on doing what you’ve always done

I think it’s more nuanced and can mean both, depending on what the speaker wants it to mean. Like two buddies trading insults )it could be banter or of could be a genuine insult). The tone denotes the meaning.

Do you speak Farsi? The Hindustani variant Murdabad is never meant literally.

It’s still considered gauche, i.e. they tell you not to sloganeer with it at Indo-Pak border

It used both literally and figuratively in Punjabi, Pahari, and Pashto as well.