The MSM would paint white over black if the color black made President Bush look good. The MSM determines its daily focus by what they collectively think will do the most to undermine President Bush.
So if the MSM says that the Iranian letter was a peace overture, then they are saying that not because it's what they believe, but because they think that's the angle that does the most damage to GWB.
But what the MSM is doing is of little value, especially in your line of thought that the letter should be reviewed objectively. The MSM is currently incapable of being objective.
An objective reader, knowing little else, would view the Iranian letter as a grave threat or would view the author as a madman. After all, that's the intent of the author; convert or die; we're a nuclear power intent upon wiping out the U.S. and Israel even if it means genocide for Iranians in response, etc.
The MSM sees that being objective would aid President Bush's current stance against Iran...so the MSM reports the letter instead as a peace overture.
But this is a grand case of two negatives cancelling each other out. Iran is bluffing. What Iran wants right now is time to be left alone from a massive military attack to continue developing their nuclear weapons, as well as to keep the U.S. and others occupied politically and militarily so that Hezbollah doesn't get smashed in Southern Lebanon right now (because Hezbollah is very vulnerable without the Syrian Army in Lebanon any longer).
So if Amadinajob is percieved as a madman, Iran bets that a new invasion of Southern Lebanon will be off the table; ditto for a large-enough attack to end their nuclear program.
To this end it is necessary for Iran to bluff. Iran must pretend to be the crazed nuclear power in the region...and in so doing will buy peace...for a time. After all, no one in the West would dare start a new land war while negotiating about nuclear weapons.
So in that manner the Iranian letter really is a peace overture. Iran wants both Hezbollah and its own domestic nuclear program to be left alone long enough to grow into a viable threat. Iran wants peace, but just for the moment.