If you look up to sand people, that's your prerogative but don't enforce it upon us.
And btw, they didn't bring Islam here, they brought the barbarity that they carried from the backwaters of Arabia. People like Fariduddin Ganjshakar, Ahmad Sirhindi, Abu Raja As Sindhi, Mian Muhammad Bakhsh (all of which were native to the Indus) made Islam popular.
Imagine thinking that Hinduism (specifically, the sects that venerate cows) is the only religion our ancestors followed. Jathera, Sikhism, Buddhism Zoroastrianism, even Manichaeism were all present in the Indus.
By "looking to Arabs" (your words not mine), you're maintaining it.
Jinnah was not Bengali. Iqbal was not Bengali. Rehmat Ali was not Bengali.