Islam spread from Spain to Indonesia because of its great message of equality. People who were oppressed converted to Islam as it gave them social emancipation. Only 5% conversions may have been forcible, but 95% were voluntary.
In Bengal about 60% Hindus converted to Islam because the caste system there had become totally inhuman ( see the novels and stories of the great Bengali writer Sarat Chandra Chattopadhyaya ). . So the 'lower' caste people converted to Islam in large numbers. If people are treated like dogs they will surely embrace a religion which treats them as humans.
If one reads Sarat Chandra Chattopadhyaya's short novel ' Palli Samaj ' ( also known as Gramin Samaj ) one will see how Muslims had social cohesion among themselves. If some Muslim fell ill or had some other trouble or calamity, other Muslims of the village would all rush to help him, but that rarely happened among Hindus. The same social cohesion was there among early Christians ( see Gibbon's ' Decline and Fall of the Roman Empire ' chapters 15-17 ).
In Kashmir too there was horrible caste oppression ( see Kalhan's ' Rajtarangani ' translated into English by Ranjit Pandit ), and so the vast majority of Kashmiris voluntarily converted to Islam to get social emancipation.
So Islam, by its message and practice of equality was of great benefit to mankind at one time.
But what is Islam as practised in India today ? The truth is that the so called ' upper caste ' Muslims, the ' ashrafs ', i.e. Syeds, Sheikhs and Pathans, regard themselves as superior and look down on Ansaris ( bunkars or weavers ), Qureshis ( butchers or kasais ), Abbasis ( water carriers ), Gaddis, Darzis, Telis, etc
When I was in Allahabad my daughter had a school friend who was a Syed. When she grew up I went one day to her parents and said that I regarded their daughter as my daughter, and so could I suggest a match for her for marriage. They agreed. I found an Ansari boy whose family had a huge carpet business in Bhadohi, which is a carpet belt near Varanasi. and I suggested his name. The parents told me ' Sorry, magar hum chamaron mein shaadi nahin karte ". I was shocked, and told them that I had thought there is no caste system among Muslims. They replied that they had to live in their ' biradari ', and so could not marry their daughter to low caste Muslims.
I may mention another incident. In Banda, U.P. there was a dalit young man who fell in love with a Muslim girl. That Muslim girl's family were Rajput converts. The young man converted to Islam to marry the girl, but the parents and relatives told him they would kill him if he does not stop meeting the girl. " Humne apna mazhab badla hai, jaat nahin ", they said.
In a lighter note I may mention an incident in Pakistan, which was related to me by a relative of mine in the Indian Foreign Service who often dealt with Pakistan affairs.
There was a Muslim gentleman in Pakistan whose surname was Chauhan. His son fell in love with a Muslim girl, and wanted to marry her, but for some reason the girl's parents refused. Mr. Chauhan then told his son " Hum Chauhan hain. Hum log ladki ke parents ki permission nahin lete, ladki utha laata hain " ( an obvious reference to the abduction of Sanjogita by Prithviraj Chauhan )
This is the reality of Indian Islam today.
Is this what the Prophet taught ?