To know the answer to this question, you must know a bit about Iran's history.
Firstly, the Iranians don't see themselves as Iranians but PERSIANS. Iran is a fairly recent name (1935) but the Pre-Iranian name of Persia can be traced back thousands of years and appears in the Old Testament. With such a rich and varied history, the people of Iran have a strong identity with the past and little love for the present Islamic country that Iran has now become.
The Persians are a race that constantly search for the truth. Throughout their history there has, on the whole, been a tolerance of all faiths but this was changed when the Islamic revolution took place in 1979. With the revolution came strict Shiite rule and Christians soon came under persecution. and today, Christianity is seen as such a threat that the persecution of Christians is at an all time high. But despite this, the number of "born again Christians" is rapidly rising.
To find out more, I have put a link below to a video explaining in greater detail what I have tried to paraphrase above. Part 1 looks at the history of the country and the church and gives a good background to the psyche of the Persians. I'll post part 2 next week.