Mr Amar Gill, You are right.It was because of casteism/brahamanism and misinterpretation of vedic scriptures which led to fracture, weakening and division of society thereby easy prey to barbarian/Babarians. But this misconception of hindus of india as a whole oweing their existence to sikhs or sikh gurus is not understandable and agreeable.It is agreeable for the hindus of J&K, Punjab, HP,Haryana and Delhi or some other parts of hindi north. There were no sikhs before 13-04-1699. After that they were refered as hindu militants nearly upto 1920s. It is after SGPC control of gurdwaras that Sikhs actually became a separate religion controling their affairs.
We need to understand my points in depth and details.
Sikhs did not come from any other land as "Sikhs" with a sole purpose of saving hinduism in India. They and their great gurus were sons of soil/Punjab. They were hindus/punjabis/indians beyond doubt, and question. In the absence of sea routes those days, greater punjab was the gateway to India for all the invaders.It had made punjabi community relatively better warriors than hindus of other parts of India.Even today's indian and pak armies are officered by punjabis effectively. It were punjabi hindu followers of gurus who resisted the moves of Aurangzeb.