When asked where they are from, most Sikhs (and most punjabi hindu's) will say Punjab not India. Most Sikhs will say "Mera Desh Punjab" not "India". Again, Punjabiat is a strong culture and emotion for Sikhs.
When you start accepting when they say "I am Punjabi" then its just a sign of accepting cracks in the foundation, then better start handing out Punjab passports too.