Not many of us know, that if at all, Guru Nanak was the truest Hindu this country will ever see. He believed in true essence of Hinduism i.e. “Om”, propagated as “Ek Onkar” in Guru Granth Sahib. He never denied the existence of Lord Shiva / Lord Vishnu / Lord Brahma and in fact makes a reference to them in Japji Sahib. It is also not a coincidence that the name of Lord Rama appears a few thousand times in Guru Granth Sahib. The ninth Guru, Guru Tegh Bahadur gave his sacrifice at Sheesh Gunj Gurudwara, to stop Aurangzeb from forced conversion of Hindu Brahmins in Kashmir. The Sikhs who used to be the first born in every family in Punjab, were basically created to fight against forced conversion and protect Hindus. It is not a very well known fact that when the Sikhs fought the Muslims, they had no territorial integrity to protect. It was only to fight forced conversion.
Sikhism also happens to be probably the most secular religion of the world. There are n number of Hindu and Muslim saints that all constitute part of the Guru Granth Sahib. We consider Guru Granth Sahib as the living embodiment and we bow before it, we do not distinguish between what has been said by our Gurus and Hindu and Muslim saints.