There have been wars in Sikh history where Sikhs took on Mughals and Hindu Mountain Kings. The Hindu Kings allied with the Mughals and were unhappy over Guru Gobind Singh’s rise of the Khalsa. They had pledged allegiance to the Mughals and took on Sikhs. This is ironic as the Sikhs were developing the Khalsa to eradicate persecution and forced conversions of hindus to Muslims. The selfish Hindu Kings wanted to hold onto their kingdoms and so did what the Mughals wanted them to do.
Battle of Sri Hargobindpur: Fought with Hindu Ratan Chand, who approached Mughals and attacked together on Guru Hargobind
Battle of Bhangani: Fought with Hindu Hill Rulers by Guru Gobind Singh
Second Battle of Anandpur: Fought with Hindu Hill Rulers and Mughals by Guru Gobind Singh. This is considered as joint attack of Hindu and Muslims on Sikhs. Even in first battle Hindu Kings were aidee of Mughals.
Battle of Nirmohigarh: Fought with Mughals, aided by Hindu Hill Rulers
There were other skirmishes happened in Punjab between Sikh Gurus with Hindu Diwans or Hill Rulers. Like Guru Arjan was martyred because of Diwan Chandu (a Hindu), Young Sahibzadas were martyred because Sucha Nand (a Hindu) turned case to Sedition.
Bad people are always there; Even in Guru’s house.
Guru Nanak’s sons rejected his philosophy and started his own way and never accepted second Guru.
Second Guru’s sons kicked third Guru on chest.
Third Guru’s son even reject to believe Fourth guru.
Sons of Fourth Guru reject Fifth Guru and even tried to kill son of fifth Guru.
Son of 7th Guru went against father’s expectation and distorted Sikh philosophy before Aurangzeb.
All these family members became parallel Gurus and participated in conspiracy against Sikh Gurus.
Also it is preached around that ‘Muslims’ were bad to ‘Sikhs’ or Sikhs were created to Kill Muslims, which is absolutely wrong and not according to Gurmat.