Re: Durand-Line and Pakistani-Occupied Afghan land.
The flaw with that argument is that the silence of the majority of the population of the NWFP and Balochistan indicates that regardless of the injustices of the past - they want to be part of Pakistan 
There is no separatist sentiment in those provinces with a large scale following, as was the case in Bengal. The overwhelming majority of Pakistan’s Pashtuns seem happy being part of Pakistan rather than Afghanistan and as such Pakistan has a duty to defend them against the small separatist minority.