Guru Nanak founded the Sikh religion in the 16th century. Born as a Hindu, he was an advocate of pure monotheistic doctrine of the Upanishads. He spent his entire life preaching his gospel of universal tolerances based on all that was good in Hinduism and Islam. While advocating a middle path, Guru Nanak exhorted his followers to discard hypocrisy, selfishness and falsehood. On Baisakhi day of 1699 at Ananthpur, Guru Govind created a new brotherhood called Khalsa (Pure Ones). Sikhism advocates monotheism, denounces caste system and believes in equality of all.
Please remember, all religion on this earth gives the same message to human being.
But it is very sad, that some of our spiritual gurus (in different religion) are not always preaching to prove that....