Someone should write a book that explains the politics of this very carefully and its cultural and historical basis. Pakhtun ethnonationalists and lar aur barists tend to take the general naivety of Pakistanis as a way to lie and manipulate their way into fooling the general population. The Pakistani establishment and media has kept this conflict covert and paid no public attention to it, the masses are simply unaware to the intricacies.
The tribalistic, hooliganisic and cultural hatred/racism tendencies are much stronger in Afghan Pakhtun populations for obvious reasons - historical culturally baggage of racism passed down, and the extremely predominant lar aur barist ideology. Historically they are brutes as seen by passed waged insurgencies and would likely launch mass suicide bombing campagins in Pakistan if felt emboldened - this is a serious threat.
Tajiks tend to be far more progressive, hence exhibit less personal racism, and lar aur barism is much less common as obviously they are not Pakhtun, after exhibiting racial injustice I doubt they want to more than double the Pakhtun population in Afghanistan!