It's a Sunni/Shia thing.
Pakistan is Sunni, with a minority shia population.
Iran is almost all Shia, with a few Sunnis.
The Sunnis consider Shias heretics, like the Catholics consider Protestants heretics,in Christianity.
The differences in Islam and Christianity results in much harder and aggressive results in Islam. You kill heretics and Infidels in Islam.
Christianity is a much milder religion, love you neighbor no matter what his beliefs, be kind and helpful forgive and forget; so the Christian differences are not as volatile as those in Islam. - tom
In the past century, you may be right about Christian kindness, but you have to thank back to all the nastiness a few hundred years ago, and even a thousand plus years ago. I just finished reading a book about the Ostrogoth king Theodoric who tried to restore Roman civilization throughout Europe. He was an Arian Christian, and Rome and Constantinople were Catholic. He supported tolerance and governed tolerantly. He even gave Jews ordinary rights. The Arian heresy was eventual destroyed. That was in the 500s. The Muslims are stuck back where we were when Martin Luther opposed the Catholic church.
Tell that to the Cathars and the millions killed during the inquisition and holocaust, and other calamities.