Pakistan believes it to be a vital national interest. Every nation gets to pick their own positions on such things.

It is typically when the U.S. presumes to impose our vital national interests onto or over the vital interests of others that we tend to get into conflicted positions such as we are now with Pakistan.

This is not about the ISI or the Army, they are agents of this vital national interest, not the determiners of it. Similarly this is not about "rights." There are many who would argue the U.S. had no right to assist the Northern Alliance in their victory or to invade Iraq. But the U.S. relied upon our belief we had a vital national interest at stake, and that no one could stop us from enforcing it. I suspect Pakistan feels much the same way in regard to Afghanistan.

This is a game that every nation gets to play. Increasingly, non-state actors as well.