Sikh sect became essentially ant-Muslim when Mughal emperors executed their Gurus.....the founder of the sect, Guru Nanak was from the period of Sikander Lodi and Ibrahim Lodi, and Afghans were not disturbing the man. The first Gurus were jogi type harmless people with few followers but some one gave false reports about their activities to jehangir (who himself was drunken man) and the latter executed their Guru.....then in Aurangzeb time, it was reported to him that Sikhs have established fiefdom in Punjab so he also acted against them....Then their last Guru Gobind invented martial code of Khalsa , turning his followers into militants. Guru Gobind's two very young sons were executed by a Muslim officer of Aurangzeb......which did it, they turned total anti-Muslim. The next leader Banda Singh was purely anti-Muslim, who either killed Muslims or left them alive after humiliation.....Sikhs turned to plundering and looting as they could not do farming in their confrontation with Mughals .....so in entire 18th century, their bands were plundering and pillaging from U.P to Sutlej and would attack muslim village or mosque whenever they were in the mood of doing that. Ranjeet Singh actually 'calmed' them down and disciplined them. If they became little bit tolerant towards Muslims , it was because of Ranjeet Singh who had empire to run, not a plundering band.
In Guru Nanak times, it was amalgamation of Hindiusm and Islam, but his successor Gurus removed most of the Islam bits due to anger against Mughals and included even more Hindu bits.....thats why British used to consider them a sect of Hinduism rather than a separate religion.
