Pacifism has a moral strength to it that having bigger guns or a more dedicated military outfit lacks.
Nelson Mandela and the other giants of South Africa were able to overcome Apartheid and systemic discrimination; Mahatma Gandhi was able to defeat the British Empire, and the Rev. Dr. Martin Luther King Jr. and the others were able to triumph over white America because they stood their ground and allowed themselves to be beaten, not once but repeatedly. Their calm, self-sacrificing moral sanity threw the insanity of their oppressors into stark relief, and brought the issue to the point that their own, oft-ignored voices finally were heard.
I think it was Romania back in the early 1990s that showed a determined and wholly unarmed populace was able to overthrow a despotic communist government with all the guns.
You say it doesn't work with Hitlers or Stalins or Arafats or Mao Tse-Tungs. I say, in the end, it's the only thing that does work.