Well, as in case of Afghanistan, where there is infighting among different tribes, races etc, demonizing pakistan will provide a bigger stronger enemy which will unite the afghans against Pakistan. People across the durand line have similar culture and traditions, they have intermarried among the tribes making that border area to have common links, but lets not forget similar situation of common culture stuff existed (offcourse on a smaller amount) in indo-pak border areas too but was very easily replaced by nationalism. If the Karzai government can play it's card right, and coerce pakistan into fighting back at durrand line, there will be sympathy for afghan forces across the board and then the same version of religion which was used to destroy afghanistan can be used to unite against pakistan.
This might be the golden oppurtunity karzai has been waiting for, have a disciplined officer corp in military wing, so that the top level is not radicalized. Create offensive against pakistani army, start maneuvering afghan taliban to move in the lines of TTP as cannon fodder. Pak army if has to fight afghan taliban at any instance, they will demolish taliban in all out fights.
It could result in better integration of afghans, especially the new generation, effectively dismantling afghan taliban threat, ensuring propping up of existential threat from pakistan which will lead to heavily centralized form of government (similar to pakistan viz-aviz India), Ensuring continued support from India.
From pakistani perspective, they need to do the exact opposite, they need to get back in talks with taliban and keep supporting those idiots to topple the government in kabul. Also they need taliban to engage afghan troops in the durand line to do the dirty work for pakistan and keep playing the non state actor game. ISI's role is crucial to afghan situation.
Afghanistan is our territory, remove the D.Line for good,whats wrong with that?
What now? Did I miss something