Sikhism was made on the basis of helping other people and you have to look at the time phrase. Guru Nanak Dev ji believed in nonviolent ways and condemned Babur for being a brutish king. Sikhism was forced to adopt to the change which still was not to praise violence, but to protect the people. Mugal kings were prosecuting Hinduism and Sikhism, which demanded that all religions should adopt Islam. During the time of Guru Hargobind Sahib the 6th guru the Mugals were tearing down all the temples, Guru ji stood against the oppression and took over and could only use force as the way to stop it. Sikhism never believes in killing and in fact Guru Gobind Singh ji never killed his prisoners. Sikhism is one of the religions that never committed murders over other religion. Sikhism is always a religion in which all are equal and believe that no one has right to force their beliefs by use of force.