Killing of an unarmed person, that too by the persons who were assigned to protect, would never have been approved by Guru Gobind Singh ji or any of our Gurus whatever might have been the provocation or motivation.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=29986
But that in no way justifies the organised massacre of innocent, poor and defenseless Sikhs. I had been to the resettlement colonies which were targetted and I was surprised to find the images of Hindu Gods both on paper and cement
were also scattered among the ruins. That means the Sikhs who worked mostly as artisans like carpenters, bricklayers, blacksmitths etc, worshipped Hindu gods also and yet they were the people who sufferred the most.
Reference:: Sikh Philosophy Network http://www.sikhphilosophy.net/showthread.php?t=29986
Gurufateh