It's just practical politics and war strategy. Why do you think we are in bed with the Pakistani's? It sucks and we should be better than this but the reality is that the world is a dangerous place and there are millions of people who wish us harm. they are the only group in Iran.
I use to feel that our moral standards should dictate who we are friends with in the world. After 9/11 thats a luxury I'm not willing to risk. We have to deal with bad guys who have the same enemies we have. Real old school, my enemies enemy is my friend.
If you don't have a seat at the table, you're probably on the menu