Tibet was never integral part of India like Kashmir. It was a territory that became part of India due to a british agreement between then Tibet government and british.
Kashmir was integral part of India since we know of India. It is source place of key pillars of Indian culture. The name itself is based on Rishi Kashyap. It is cradle of Sanskrit and Sanskriti. Until terrorist invaders came 700 years ago, Kashmir was as Indian as Varanasi. Then agenda of rape, murder, forced conversion happened to change demography.