Someone who believes in the sacredness of human life most perforce support violence when that violence will clearly save many lives. We don't need to look hard to find historical examples. Had the social democrats used the violence of the state that was put into their hands in 1918, Hitler could not have come to power. Had the Stalinists not withheld arms from the Spanish working class in Madrid, Franco would have fallen early and the Spanish Civil War would not have dragged on. Or, for positive examples, the defense of the Greek city-states against the Persians, who were in the habit at that time of killing civilians in the tens of thousands; had the Bolsheviks refused to use violence to lay hands on state power in 1917, the Kornilovists would have slaughtered the St. Petersburg working class.
Someone who believes that one ought never to use violence because of the spiritual damage it does the perpetrator must give countenance to the most appalling acts; in all of the examples given above, he must necessarily oppose the action that did or would have prevented the salughter. His reaction to Franco, to Stalin, to Hitler, would be something like, "He shouldn't have done that," after telling those who could have stopped them not to do so.
Any moral code that attempts to set itself up as an absolute--above society, something good for all times--faces insoluble contradictions, because morality is the product of social development. In the case of pacifism, these contradictions are blatant.
"When enlightened pacifists try to abolish war by rationalistic arguments they are merely ridiculous, but when the armed masses themselves bring weapons of reason into action against a war, that means that the war is about over." -- Trotsky.