Nice thread Ben. You are a true Christian, and that perhaps is one of the highest and rarest compliments that i would or could give to a person. I would like to visit Iran someday, i have some connections to there in a way.
Becky and i went to Turkey (and Greece) a little while back. It was nice, the Turkish people were nice and helpful. It's amazing how surprised and appreciative people are when you try to learn at least a few words of their language and speak it to them.
Sure there were and are some cultural differences, but as others have noted, people are people and i think most of us are decent hearted people, or at the very least a curious admixture of light and dark (metaphorically speaking).
We couch surfed in Istanbul with an interesting, and overall nice/considerate guy. Good to get a local perspective--granted though, he is an atheist and wasn't/isn't a fan of Islam or any religion. I realize Istanbul is considered more liberal than many other Islamic cities, but in ways it was still fairly foreign on the surface for us.
I will say in our travels though, i have seen some Americans in other countries and have been kind of, well not quite embarrassed, but very cognizant of the American stereotypes because i saw them first hand. But then again, i've seen some pretty darn rude, inconsiderate, and LOUD folks from other countries in other countries different than their own. Especially staying in hostels... So yeah, people are people with small, minor differences on the surface.