Muslims in India are very treachourous. Wherever muslims are in majority in India, they actively work against India. During partition, muslims of Hyderabad demanded to join Pakistan, thanks to Sardar Patel who could forcefully crush the demand and prevent the separation of Hyderabad. I have seen how defeat of India at the hand of Pakistan in cricket matches are cellebrated as a diwali in Hyderabad.
Now muslims are fighting in Kashmir to join Pakistan. Very soon this will spread to other parts of India wherever these muslims are in majority.
This is why Islam is the biggest threat to our national integration.