I had a discussion once with a group of Indians and the obsession is not just limited to 'Pakistan' alone. The Indians claim the entire sub continent as an integral part of 'India' as well as the entire history and the Ocean around it, (The Indian ocean).
I guess it comes down to how you would term the word 'India'.
In the words of the British Prime minister Winston Churchill, "India is a geographical term. It is no more a united nation than the Equator".
The Indians beg to differ...
They claimed that India was not born in 1947,
and that Pakistan and Bangladesh was India and that Sri lanka, Bhutan and Nepal were always a part of Indian heritage, (by religion, diversity and values).
OBSESSION YOU WOULDN'T BELIEVE HUH...!