Just look at Iraq for example. Bush (further perpetuated to the public by the media) repeatedly depicted the “Terrorists” as this homeogenous, desert-dwelling, bearded, self-combustable enemy that lives in every Muslim country in the world. Iraq, Iran, and Afghanistan were all just part of the same enemy, and he acted on that assumption. Look at Iraq now, a chaotic three war civil war that starting to drag the Middle-east into five rival camps: Israelis, Shiites Arabs, Sunnis Arabs, Kurds, and Turks. Bottom line as you tersely put it, we need to proceed carefully in Iran and be aware of all the subgroups and potential consequences.