Caste itself is a religious concept, which btw is not limited to Hinduism in India, even Christians practice it:
The Constitution of India forbids discrimination on the basis of caste and provides many measures for affirmative action for the upliftment of people who have been oppressed for centuries. I simply don't understand how caste -> ! secular. What does secularism have to do with nukes anyway ?
The British monarch, who is also the head of state, has to be a member of the Church of England. There is no such restriction in India, where we have had Hindu, Muslim and Sikh presidents. We have also had a Dalit president. So British 'secularism' is good enough for you but not the Indian variant ? Nevermind that in post WW2 US, blacks didn't have the right to vote ? Was the US non-secular for 250 years of its existence ?
China and Russia too have their internal troubles and are by no means 'peaceful'. France recently had a lot of riots carried out by immigrants. Do you propose that they give up their nukes since they don't meet your criteria of being peaceful?
Pakistan, a country ruled by military dictators with Islamist leaning, the birth place of the Taliban who carried out 911
... how can you even compare it to India ?! Pakistan is MAJOR nuclear proliferator. Just google AQ Khan for the details.