What legitimate interests? Up until recently, the interest was in helping the Taliban and now it is fighting the Taliban. The NA has always been fighting the Taliban, so you're essentially on the same side now.
Pakistan's legitimate interests in Afghanistan were:
1. To disallow the Soviets from taking over the country on account of a) brotherhood with the Afghans b) so that the India-Soviet Alliance would not surround us and c) so that the soviets would not attempt to invade Pakistan to obtain access to warm water ports.
2. To prevent the transit of illegal drugs into Pakistan; in the '80s and '90s Afghan drugs caused a lot of misery in Pakistan on multiple fronts
3. To help in creating an environment that would allow over 4 MILLION afghans who are residing in Pakistan, to return to their own country. There is no way in hell we should have to sustain this massive burden that has been placed on us since the last 30 years.
4. To prevent conditions that would allow Pakistan's enemies to use Afghanistan as a base against it.
And there are numerous others.
It is ill-informed, short-sighted and incorrect to suggest that Pakistan's "interest" was in supporting the Taliban. This was never the interest. The interest was to put an end to the infighting. The NA had been tried and they had failed. Just look at what they did in Kabul. The Taliban were up and coming and had become incredibly popular in the South. They had a lot of successes behind them and appeared to be gaining traction amongst the *people* of Afghanistan. Just go back and look through the old newspapers that show Kabulis celebrating the arrival of the Taliban. Were all of these people bribed by Pakistan? No. They were genuinely fed-up of the NA who had raped, plundered and murdered like devils.
To say that the NA has always been fighting the Taliban is tricky on two fronts; many elements of the Taliban of today were allied with what is now referred to as the NA when the Soviets were in Afghanistan. Secondly, the Taliban were a movement in part spurred on by the behaviour of the NA warlords. So obviously, it was in the NA's interest to fight them. As I have said previously, it is another matter that the Taliban also ended up being swines. That fact dawned upon everyone much later... one must be careful about hindsight.
Are you saying that NA who are arch enemies of the Taliban, are funding the Taliban?
You need to shore up your comprehension. I never said this. I said that the NA is allowing India to use Afghan territory against Pakistan. And India is using anyone they can find to foment trouble in Pakistan. Does this equal the NA funding the Taliban?
