Let me make 1 thing very clear, we may call ourselves Mohajir (migrant), but we are the ones who gave you freedom from both the English and the Hindus! If our ancestors could take freedom from the English, you guys are less than peanuts!!!
However, it is not about separating Karachi from Sindh, it is about self governance. Illiterate Sindhi win from interior Sindh, rape interior Sindh but in the same course of action they also rape Karachi. While you may enjoy all that, we do not. Under self governance, we can take Karachi, and ultimately Pakistan, to new heights which you can not even imagine.