Iran is Persian, not Arab.  Their theocracy is Shi'a not Sunni. 

 There are not 'two sides' in the Middle East; there are hundreds of years of animosity between the Arabs, the Persians, the Kurds, the Druze and each other.   You must think 'tribally' to even have a hint of the conflict(s) involved.  

We 'Crusaders' are just one of many groups to be hated, reviled and feared.   Jews and Christians were once "People of the Book" and not targets of jihad.    That has varied throughout history depending on the power seekers of any particular century, including this one. 

"My Brother and I against My Cousin; My Cousin and I against the Stranger." is a widely adopted concept across the entire region .  Unless you understand that concept you are ignoring a fundamental fact of life.