Re: Why Do Pakistanis Reject their Indian heritage?
Some Iranians ("Westernized") tend to be racist based on their ignorance and false sense of superiority complex. Some of them would even make bigoted comments against Baluchs, Pashtuns, Afghans, and Arabs...calling them savages, dark and ugly. So their rejection is not limited to Pakistanis, and goes much more beyond including its own citizens/minorities. But we should not stereotype all Iranians based on these forums/etc.
Most importantly, Iranian is the same word as Aryan, so the present-day country of Iran does not have a monopoly on this proto-ethnic and historic terminology. The people of Tajikistan, Afghanistan, Pakistan, Iran, western Turkey, northern Iraq, northwest India, and parts of Central Asia are descended from ancient Iranians/Aryans... this includes their language, culture, and race. Of course those ancient Aryans/Iranians were mixed with other peoples/races over time, but they have by large retained their unique traits through the process of evolution. Besides the ancient Aryans/Iranians, there is a lot of other shared heritage in the region such as those under the Achaemenian, Greek, Scythian, Hepthalite, Arab, Turkic, Mongol, etc. periods.
Now whether a racist/ignorant Persian rejects a Punjabi for being a shade darker and denies sharing a common heritage then thats just nonsense, and deserves no attention. The fact is historically the people of Pakistan have been much closer to its western neighbors (Afghanistan-Iran-CAsia) than to its eastern neighbor (India). And then Pakistan inherits its own unique and great civilizations based on the Indus Valley such as the Harappans, Rigvedic Aryas (Sapta Sindhva), Gandharans, etc.
Just in the past one hundred and some years ago with the arrival of the British an "Indian/Hindustani" identity was created with Urdu/Hindi (Gangetic) culture as its foundation and promoted to other regions under its rule. This trend has continued after Pakistan's independence due to the domination of Muhajirs (carriers of Urdu/Hindi culture) and their promotion of it via the media, govt, schools, etc. Similar concerns are in India with Tamils, Nagas, Sikhs, etc rejecting the Hindi-Urdu (i.e. Hindustani/gangetic) cultural imperialism, and fighting against their on-going cultural genocides.
India (British-created/promoted "Hindustani/gangetic civilization") is no model for tolerance, freedom, etc. Ask the oppressed Nagas, Tamils, Dalits, Muslims, Sikhs, Kashmiris, Manipurans, Tripurans, Mizos, etc. on their plight in India and then we can see a clearer picture.