I don't think that saying "I'm ashamed" when in face of cruelty, or what is called inhuman treatments, guilty is not the most important sense of the word shame.
It is the word that was chosen, I don't know when, to express the perplexity and bewilderment that some events cause. The expressions
"crying shame": Fig. a very unfortunate situation. and
"What a shame!" Fig. an expression of consolation meaning That's too bad." "What a pity!" has the sense of "It's to sad." to the word "shame".
It is not a question of blaming ourselves, not a moral issue.
But for those who don't like seeing horror spectacles, or have pleasure in seeing misery, the felling "what could I have done to prevent it?" can be hidden somewhere. No. Not guilty or helpless will take over and this is not a good combination.
The best to do is to turn this bad conscience into action. Nunca más**!
*Picture: "Shame," by Ori Kleiner, 21 May 2004 via oznik-art.
**(English: Never Again), the title of the 1984 report of Argentina's National Commission on the Disappearance of Persons