Why did the US give a legion of merit to the captain who shot down the Iranian passenger airliner?

A U.S. naval fleet in the Persian Gulf shot down an Iranian passenger airliner with about 300 people on board. They said it was by mistake. To hell with you for making such a grave mistake! If the commander of the fleet made a mistake, why did you give him a legion of merit?!

July 4, 1991

From the initial hours of the Revolution, this enemy revealed its presence and expressed opposition [towards the IRI]: this enemy was the government of the United States of America. From the very beginning – of course, I mean after recovering from their initial confusion, following days when they had no clue as to what was going on – they began to oppose us and show their hostility. To this day, while we speak, the Americans [from the USA] have employed numerous plots, methods, and means of deception aimed at striking the Islamic Republic. Indeed, there is no hostile method that they haven't tried against the Islamic Republic!

They organized military coups; they provoked ethnic groups to turn against one another; they provoked Saddam into attacking and fighting against Iran. During the war [8-year Holy Defense War], they supported Saddam in various ways, and they imposed sanctions on us. The US government powers used their influence against Iran within the UN: they launched propaganda campaigns, day and night, and they used their knack for mischevious planning to further their goals [against Iran]. They used their Hollywood industry to make anti-Iranian films – and not just one or two. The USA launched military moves in various strategic regions: they shot down our passenger plane and attacked some of our centres in the Persian Gulf. The USA government has manoeuvred all sorts of schemes against the Islamic Republic: they have mounted security, political, economic, propaganda, cultural and various kinds of oppositional operations. 

And the purpose of all their [USA's] manoeuvring was to overthrow the Iranian government. If today, this idea [to overthrow] is being echoed in the statements of American officials, this is not a new concept: this was their goal since day one [of the revolution]. Their previous president [Barak Obama] who kept announcing that their goal is not to plot a coup, he even pursued a goal to overthrow [Iran's governing body]; of course, his motives were completely transparent