But we must apply an equal standard to all, thats the very basis of a society of law and justice.
You have to use facts, not your imagination, in determining who is trustworthy and who is not. Iran (as an Islamic State) has AFAIK not once ever attacked a foreign nation. Not once. Iraq actually started the Iran-Iraq war by invading, so that doesn't count.
Now, lets look at the US. Starting from the present day and working backwards, we have: Iraq, Afghanistan, Kosovo, Desert Storm, Grenada, Nicaragua, Lebanon, the Bay of Pig, Cambodia, Vietnam, Korea etc etc.
And this is not counting the various proxy wars (Afghanistan in the 80s, Columbia) or support for genocidal wars (Indonesia) or coup d'etats (Venezuela, Haiti, Georgia, Chile, Iran, Guatemala etc) I'm sure I'm forgetting some, but this seems like plenty.
I have no reason at all to believe that Iran would attack another country, much less use nukes, because they have not shown any signs of external agression (not counting internal repression which I by no means support).
So, who do you trust more, a nation who in its current incarnation (and to the best of my knowledge, all previous incarnations) has been peaceful, or a nation who can't go 5 years without starting a war?
edit: the only agression I can think of is the taking of the hostages, who were later released and in any case, you have to expect some retribution after decades of the Shah's rule. Also, considering how Reagan & Co worked to prolong the suffering of the hostages for their own gain, I wouldn't exactly say all you Bushies have the moral high-ground.