It happens because Indians do not identify with India. Our primitive, oppressive society has prevented its so called members from feeling like Owners or being a part of it. Merely lecturing people about benefits of National Unity is not enough. We have to actually practice Unity first, i.e., consider everyone's interests equally when arranging our National Affairs.
Display of Unity arising from Rousing Speeches in times of War has misled us to believe that we are a United Nation. In fact we are not a Nation at all. Everyone who lives here is in for his piece of the cake, and devil take the Hind Most. No one wants to return anything to the Nation because they are all Tenants or Exploiters not Owners.
