Certainly, the racist approaches as well as national and religious prejudices are from the greatest impediments of cognition and the causes of disagreement among Muslims, while Islam with its own emergence has terminated such ignorant glories, and has removed fabricated boundaries from among the human beings and declared faith as the basis of brotherhood and infidelity as the basis of hostility, but unfortunately it seems that some Muslims are still in ignorance and have not fully entered into the Islam.
With this introduction, we draw your attention to the following notes:
Firstly, contrary to your notion that “a few people attribute this problem, meaning the extension of Islam by leaning on the sword, to the Messenger of God”, many in the world attribute this problem to the Messenger of God (peace be upon him), and with an approach similar to your approach about the companions of His Excellency, consider the personality of His Excellency, because of works such as attacking the civilian convoys of Mecca, expulsion of Bani Qaynuqa and Bani Nazir from Medina and mass execution of Bani Qurayza, as militant and seeking extension of Islam by leaning on the sword, and to prove their claim, refer to the verses of Jihad In the Qur'an and their conflict with what they call human rights, while their claim is abrogated and biased and has been answered in detail on its own place.
Secondly, in your appendix, you have denied “the extension of Islam because of its attractive teachings” and have said: “Which Islam?! The Islam which lacks its most important principle, meaning the Welayat of the Caliph of God, and its leadership is exercised by unqualified individuals, and base on the Qur'an’s interpretation Taughut” while this speech is delusional and inaccurate to the ultimate extent; because although the Welayat of the Caliph of God on earth is one the principles of Islam, but there are other principles such as prayer, fasting, zakat and hajj after believing in monotheism, prophecy and resurrection, and with this description those who believe in these principles, even though they do not know the Caliph of God on earth, they are Muslims and consequently can help to extension of Islam around the world by presenting its attractive teachings; especially due to the fact that Islam is better than infidelity in any case, and cannot prefer infidelity rather than that even to the extent of Shahadah.
Thirdly, you claim that “the comparison of Iran and Rome is completely wrong”, because base on your notion the Iranians were monotheist and Romans were unbeliever, while this is a racist and unscientific speech; because in Shari'a, both the Iranians and the Romans were non-Muslims and were from the people of book, and with this respect, are considered as unbelievers and subjected to the rule of the «الكُفْرُ مِلَّةٌ واحِدَةٌ»; but the Iranians were Zoroastrian and Romans were Christian, and Christians are more from the book than Zoroastrians, and for this reason, the attitude of Islam and Muslims has always been better toward Christians than Zoroastrians. Moreover, the Roman king's treatment with the Prophet's invitation was much better than that of the Iranian king; since Heraclius the Roman king, after receiving it, respected the Prophet, and by summoning a group of Quraysh, investigated about His Excellency and ultimately has not denied him, but count him a prophet, but Khosrow Parviz the Iranian king tore down the invitation of His Excellency, and beside insulting His Excellency, said to his messenger, “If you were not the messenger, I would behead you”, to the extent that in some famous narrations, the Prophet cursed him and asked God for the decline of his kingdom! With this description, it seems that if the comparison of Iran and Rome is wrong, it is because Rome was superior over Iran, and this is contrary to your claim; as in the book of God also when the Romans victory over the Iranians was promised (Surah Roman, verse 4), apparently, the happiness of the Muslims about that is reported, and this is, based on some narrations and the famous opinion of commentators, due to the Romans superiority over the Iranians in the opinion of Muslims.
Fourthly, with your national and racist prejudice, you have claimed that “the Muslims' insistence on the conquest of Iran after the Messenger of God seems surprising”, while considering above explanations, it is not surprising, because the Iranians' attitude toward the Arabs Muslims was much more worse and humiliating than the Romans’ attitude, and their religion, according to Islam’s opinion -contrary to your claim-, was more wrong; as the Islam’s laws in chapters such as sanctification, marriage and slaughter were often stricter pertain to Magians than its laws pertain to Christians. Furthermore, It is Mutewatir and well-known that the Prophet of God (peace be upon him) has announced in many occasions the conquest of Iran and Rome by the Muslims and their domination over the treasures of Kasra and Kaiser, and it is interesting that in all these cases he has mentioned “Kasra” before “Kaiser”, as for instance, in battle of the Trench, when with his blessed hand heat the ground with a pickaxe and broke a large stone, said: «لَقَدْ فُتِحَ عَلَيَّ فِي ضَرْبَتِي هَذِهِ كُنُوزُ كَسْرَى وقَيْصَرَ»; “For me in this heat of mine the treasure of Kasra and Kaiser are conquered”! Therefore, there are many narrations showing that Muslims, in moving toward Iran before moving toward Rome, had expectation about this promise of Messenger of God (peace be upon him), and expected the victory over Iran before the victory over Rome.
But your strange claim that “Rome was never conquered because the Muslims’ Caliph had no interest in its conquest” is either due to your ignorance or to your extreme prejudice; since the Muslims during the time of Abu Bakr, simultaneous to conquering part of Sassanians’ territory, also fought against the Romans and conquered the Levant, to the extent that they occupied Palestine and surrounded Damascus, then conquered areas of eastern Rome during the time of Omar bin Khattab such as Damascus, Baalbek, Homs, and Yarmouk. To the extent that Heraclius the Roman king abandoned the Levant and fled to Constantinople, and the Muslims could gradually dominate across the Levant, and even proceed to the Taurus Mountains in Asia Minor. In addition, they, during the time of Omar, conquered Egypt which was under the control of Roman, and proceed, during the time of Uthman, even to the Strait of Dardanelles in the Marmara Sea and fought with the Byzantine armies. It is understood from here that your claim that “the lack of Muslims’ insistence on conquering Rome unlike Iran” and “the lack of Caliph's desire to conquering the Rome” is simply an illusion arising out of your national and religious prejudice.
Fifthly, In the rest of your appendix, you have denied the extension of Islam because of its attractive teachings, and by referring to Mongols’ domination over Iran, have claimed that the extension of Islam was based on the sword of the Muslims, while this is also a strange fallacy and an irrelevant comparison; because in the above question and answer, the speech is not about Muslim domination over Iran, but about the extension of Islam in Iran, which was certainly due to its attractive teachings, not the sword of the Muslims; considering that in the attack of wild and infidel Mongols to Iran, the Iranians have never accepted their religion, but after a while they turned them into their religion, but in the attack of Muslims to Iran, Iranians accepted their religion quickly and after a while became sincere Muslims and provided many scientific services to Islam. It is understood from here that the Iranians never became Muslim because of the sword of the Arabs, but became Muslim because of the attraction of Islam; because if this heavenly religion were not attractive to them, they would have never been submitted to that, just as they have not been submitted to the Mongols’ religion. With this description, it seems that you are trying to respect your people, but you are unknowingly giving them the biggest insult; because you claim that the Iranians converted to Islam, not for the rightfulness of Islam, but for the Arabs’ sword, whereas we consider this claim false and believe that the Iranians have accepted Islam because of its rightfulness; especially considering that contrary to your illusion, Muslims have not forced them to accept Islam, but they left them free to accept that or accept Jizah. At least, during the time of Abu Bakr, Omar, Uthman and Ali, the laws of Islam about war, peace, Jizah, Amman, captives and trophies were regarded briefly, and it was only during the time of Bani Umayyad and Bani Abbas that they probably did “crimes such as murder, rape, insulting, humiliating, burning scientific books, killing Iranian scientists and their ruthless treatment toward Iranian women and girls, in which the tongue shames to speak about it”, and therefore, there must be distinguished between the conquests of the companions of the Prophet (peace be upon him), which was sometimes accompanied by consultations with Ali ibn Abi Talib and the presence of individuals such as Salman Farsi, Hozayfat ibn Aliman, Muqdad ibn Sa'ud, Hashim ibn Atabat, Ammar ibn Yasser, Hijjr ibn Adi, and Bara ibn Azib, and the Umayyad and Abbasid conquests.
Furthermore, it is surprising that you consider wrong the comparison between Zoroastrian Iranians and Christian Romans, but you do not consider wrong the comparison between Muslims and irreligious savages similar to Attila and Mughal Genghis khan!! We seek God's help against these racist attitudes and national and religious prejudices, which are one of the greatest impediments of cognition and the causes of disagreement among Muslims.
We advise you Muslim brother that with complete obligation to the cognition standard, and complete avoidance to its impediment, make your mind free from these illusions and passions, and do not be influenced of the propaganda and inductions of anti-Islamist and divisive bodies, and consider Islam as the only basis and standard for your beliefs and actions.
We ask God for your mercy.