A fair few things.
1) Motive. The only party who stands to gain anything from this measure is the Pakistani military. Correction: The Pakistani Afsar. The politician has nothing to gain from it.
2) Counterproductive for the politician. The Pakistani politician is only second to the military afsars in the Pakistani hierarchy of things. He is also, more often than not, the target of the military's whims. By passing this bill, he is shooting himself in the face. Hence the reason why no politician has ever supported any measure of this sort in Pakistan's history. Unless, he stood to gain from the military himself.
3) If we did somehow find that one politician who is honest, then by virtue of being a legislator he would know better than to push a bill as unconstitutional as this. I, at least, would think that the politician, dishonest or otherwise, is a bit wiser to the machinations of the Pakistani power landscape than the hyperbolic posters on PDF.
4) Lack of precedence. If hyperbolic nationalists were sitting in the parliament then this would not have been their first bill. PTM, at least, would have been crispy and done by now.
5) The politician does not present any bill without a concerted backing. Never on a whim. He has "better" things to do. The vote result also shows that this was not an outlier idea.
6) We've seen it all before. Many times. And every time, we did not have any evidence until decades after.
