Ok, I'll write a more serious and less pissed off wall of text here. I should add that I'm currently studying Arabic and the Middle East at Stockholm University. A large part of my education is the religions and history of the Middle East, with less emphasis on other regions. Because my focus is Arabic, I've read a ton of Arabic history. I should also add what my disagreement with your attitude is, since we're going around in circles, stuck in minutiae.

You claim that Islam is inherently Arab chauvinist, citing historical examples, and you're not completely wrong. But you have also written that Islam has spread only because of conquest, which is demonstrably wrong. So here is a brief overview of what I've learned about the spread of Islam and the role of Arabs:

The Umayyads were Arab supremacists, yes. But it's important to understand what this means. The Arabic society before Islam was a clan-based nomadic society with a small clique of wealthy settled people engaging in trade. As the Arabs expanded, they started to embrace the culture of the conquered peoples, as often happens in history. Many Arabs started settling, which created a split in Arab identity. On the one hand, the settled Arabs in the Fertile Crescent, and the other the traditional nomad warriors who wanted to continue waging war. The other factions in Umayyad society were the malawi, non-Arab converts to Islam, and non-Muslims. The Umayyads wanted the Arabs to be a ruling class, and considered themselves more worthy, claiming that they had inherent authority since Islam was revealed to the Arabs. The Malawi, especially Persians, cited other parts of the Qur'an and hadith that called for a worldwide umma.

The Qur'an and hadith have contrary things to say about this. On the one hand, as you correctly point out, they celebrate Arabs and contain explicit racism. It's also important to note that the Arab that is being celebrated is the traditional one, the bedouin, the warrior poet. It's pretty damn far from what Arab identity evolved into, but I'll get to that. On the other hand, there are calls for a universal umma. Both points of views have been argued with Islam as a basic premise.

The Arab chauvinism was a major part in the fall of the Umayyads. The Abbasids managed to obtain the help of malawis, which was one of the deciding factors. The society and identity that developed under the Abbasids was completely different from the Umayyads. You say that Persians had been arabised - actually, the Arabs were increasingly persified. There was no cosmopolitan culture native to the Arabs. The culture and identity the Arabs in the Fertile Crescent built was mostly based on Hellenic and Persian thought. Greek and Persian works on philosophy, religion, administration etc. were the staples, and the clerks of the Abbasid administration continued to be Greeks and Persians for a long time. This is when Islam moved away from an Arabic religion to a world religion. The core texts are still in Arabic and are not meant to be translated, and a fundamentalist would argue that Arabic is the language of God. But the Islamic society was developed in a syncretic environment based on Persian and Greek civilisation.

The spread of Islam was slow in the conquered regions. It was discouraged by the Umayyads, encouraged by the Abbasids, but mass force conversions were rare. They did occur, as I'm sure you're ready to point out, but the fact remains that it took hundreds of years before a majority in the regions became Muslim. Syria still has approximately 10% Christians today. It's impossible to know why people converted. The most likely scenario is that people were pressured into it by the economic advantages of being a Muslim, but in a time when religion was the very BASIS of identity, to choose eternal damnation to get rid of the jizya would have been quite a leap. The mainstream consesus in the field is that it was most likely a combination of economic pressure, a general drift towards the views of the elite and some inherent attractiveness in Islam, primarily sufism for the general population. If you think that it is forced conversion when the pressure of being disadvantaged leads to conversion, then yes, you have a point, and I'll agree with that.

Another reason to convert to Islam was the vast trade network the Muslims had built, stretching from Africa to the Middle East to India and even to Indonesia and China, and the overland silk road as you know. Conversion meant access to this network, which was highly lucrative. This is probably a much larger reason than a military one for conversions in East Africa, Indonesia, etc. Still, there is pressure, but not military pressure.

The Abbasids slowly crumbled. They relied on slave armies and paying local notables with hereditary land for tax-farming, just to give a brief overview of a long and complex decline. The end result was an Arab figurehead while the true powers in the region were Persians and Turks. When it comes to the Turkish tribes, it's important to note that the Central Asian regions were not exactly modern nation states. The people who lived in Transoxiana and further north and east on the steppes were highly mobile and diverse steppe nomads. It was impossible for empires to govern these regions, and they were characterised by constant minor skirmishes and larger excursions between settled peoples and nomads. While the settlers were primarily Muslims, the nomads were a continuum of different Turkish and non-Turkish tribes, with a plethora of religions. As centralisation and cohesion declined in the Persian dynasties who had the real power east of Baghdad, they were overwhelmed by nomads. As often happens in history, large movements of nomads will rain down on weak regions, originally for pasture and looting, but if they stay, they often embrace the culture and religion of the settled people. By the time Turks became dominant around the Caspian Sea, de facto power had been with the Persians so long that the Islamic culture they adopted was completely Persian in nature, except for the Qur'an of course. This Turko-Persian mix was the dominant Middle Eastern elite culture from the 12th to the 20th century. If one examines Ottoman Turkish for example, half of it is Persian. This is also about the time where non-bedouin Arab identity crumbles outside of Africa and the western Levant. It had been completely absorbed into a general Islamic culture. Arabic identity as a political force wouldn't really resurface until the rise of the Wahhabis on one hand, and the secular, intellectual pan-Arabism on the other. During about 800 years, high Islamic culture was Turko-Persian. Islam as a society and a thought system had completely broken away from its Arabic bedouin past.

I think that the main reason why Arabic exceptionalism has resurfaced in radical Islam is due to the Wahhabis, and more importantly, the oil money of the Saudis. The Saudis, who are madhat fucking bonkers are also rich as fuck and backed by the new imperialists, great wonderful United States of Fuck the World, Give Us Oil. Since they have so much money to burn, they fund a ton of mosques and Islamic centers for learning all over the world, filling them with radical wahhabi influences and anti-semitism, to the point where this becomes associated with Islam, despite the fact that Islam is a widespread, dynamic religion that comes in tons of different forms in different regions of the world.

But now, the sufis. You should read about them. These mystics, different in every country, played a major part in the spread of Islam. Their Islam was and is a highly syncretic, mystical, at times esoteric, at times populist version. Sufism was heavily influenced by Persian and Indian thought, as well as neo-Platonism and other Hellenic mysticism. They were constantly wandering, active missionaries, providing general guidance as wise men (and even some women), writing poetry, proclaming saints for the locals to venerate and much more. Most importantly, they were always ready to incorporate the views of locals wherever they went. They were, and are, quite different from the fundamentalist rulers who based their rule on might and brutal enforcement. They were highly active in India, North Africa, West Africa and also in Central Asia and Southeast Asia. Whether they converted more or less people than armies, forced conversions and economic pressure did is impossible to guess, but it is generally accepted that they were a large part in the worldwide spread of Islam.