@ Are Bhai, it was the Dada's of West Bengal who first invented these theories that majority of Muslims of Bengal are foreign origin.
@ For your information once the muslims came in Bengal the majority of local population were Bodhu's instead of Hindus. Though the Sen Dynesty was in power. In fact in those days no convertee were allowed in Hinduism so silently the people had no faith. Once the muslim saints came either from the West or from the south through Arakan the local people gladly accepted Islam. Bengal became a fertile land for preaching Islam.
@ I give you some more examples, the forefather of Golam Azam were came from Persia. The grand father of Khaleda Zia came from Arab. The maternal blood of Khaleda Zia came from Murshidabad. Md Ali of Bogra who was the Prime minister of Pakistan came from Persia. Like wise I can give you many examples.
@ I give you one practical example. It was in the year probably 1872 when the first population sensus started in Bengal. So, the British administraters started working at Pabna district. It was surprising that none of the Bengali muslims gave their identity as Bengali. It was only the Hindus who gave their identity as Bengali. The other people wrote as Phatans, Syed, Afghans, Persian. The common people had no idea about their identity.