I find it contradictory that Muslims claim that Islam is the religion of peace yet they attacked Iran (Sassanid kingdom), killed millions of people, took Iranian women and sold them as sex slave. Is there a sound and logical explanation of this?
I don't think that u're really looking for an answer. But anyway, I answer this question without my own thoughts and just with Reasons and logic.
Muhammad wrote a letter to the king of persians ( He was called "Khosro-Parviz" ) and the letter was started with something like this : "In the name of God ... from Muhammad the prophet of god to the great king of persia" u see that he called the king properly and the letter was not to insult persians. But the king of persia ripped the letter because it was started with the name of god not his name ! So that's why they attacked Iran and let me say that Muhammad always said good things about iranians and their science. And also, What the society of arabs thought about the iranians is not exactly what Muhammad thought about Iranians.