“Savage – There is only one way fit for a man – Heroism, or Master-Morality, or Violence. All the other people in between are ploughing the sand.”

Source: Mars and its Canals (1906), Chapter XXXII, Conclusion
Context: War is a survival among us from savage times and affects now chiefly the boyish and unthinking element of the nation. The wisest realize that there are better ways for practicing heroism and other and more certain ends of insuring the survival of the fittest. It is something a people outgrow. But whether they consciously practice peace or not, nature in its evolution eventually practices it for them, and after enough of the inhabitants of a globe have killed each other off, the remainder must find it more advantageous to work together for the common good.

"Love's Servile Lot", line 73; p. 65.

Source: Dorothy Thompson’s Political Guide: A Study of American Liberalism and its Relationship to Modern Totalitarian States (1938), p. 78

The Groundings with my Brothers https://archive.org/details/TheGroundingsWithMyBrothers (1969)
Context: We were told that violence in itself is evil, and that, whatever the cause, it is unjustified morally. By what standard of morality can the violence used by a slave to break his chains be considered the same as the violence of a slave master? By what standards can we equate the violence of blacks who have been oppressed, suppressed, depressed and repressed for four centuries with the violence of white fascists. Violence aimed at the recovery of human dignity and at equality cannot be judged by the same yardstick as violence aimed at maintenance of discrimination and oppression.

Interview (1961) http://www.radiodiaries.org/mandela/t_movement.html
1960s
Context: There are thousands of people who feel that it is useless and futile for us to continue talking peace and non-violence — against a government whose only reply is savage attacks on an unarmed and defenceless people. And I think the time has come for us to consider, in the light of our experiences at this day at home, whether the methods which we have applied so far are adequate.

As quoted inThe A-V Magazine Vol. 89, No. 1 (January 1981), p. 18, and The Extended Circle : A Dictionary of Humane Thought (1985) by Jon Wynne-Tyson, p. 75; this has been cited to "Harper's Magazine (1890)" but no occurence prior to the 1981 appearance has been located.
Disputed

Source: Small Great Things