If you ask any Indian or Pakistani citizen, most would say that British rule was a cruel thing, and that freedom was inevitable.
Now, if you look at the Kashmir situation, even though India have "official documents" to prove that the whole of Kashmir should be part of India, a lot of people in Kashmir don't want to be part of India or Pakistan.
Some people claim that under India (or Pakistan), Kashmiri people won't face issues. Well, I can say that Britain also had somewhat similar views: for example, "Hindustan will be developed better under British rule". But freedom was the most important thing at that time and it was the right thing to struggle for freedom. So this reason is not good enough to justify ruling Kashmir.
So eventually, it's not about who should rule, it should be about freedom.
So how do people who want the whole of Kashmir to be part of India or Pakistan justify this belief?
Disclaimer: I have nothing against any country, people, or religion. No disrespect. I just want to know how this is justified.