He is not dreaming entirely, he is visualising. Your enemy will always look to take advantage of anything you do. Even if you buy bread he will hope you choke on it.
If a few million Afghans become Pakistani, it doesn't change a thing, but if you don't recognise them as humans, or Pakistanis, and instead focus on them by their former nationality, then you will light the flames of ethnic violence in your country yourself.
Look at muhajir from India. How much violence has Karachi faced because every day people believed the hype of "the muhajir are here to take everything from you!". We faced this discrimination nationwide, even in AJK. It's because our population is foolish and narrow minded.
If we were to conquer Afghanistan, you people would claim the land as Pakistani but want the people to all self immolate. When we had East Pakistan, the land was Pakistani and the people were dirty little Bengalis. Look where that mentality led us.