It's not genocide, at least not yet (as distinct from "genocidal acts"… perhaps not for all that much longer). It's "just" an atrocity. Yes, in fact one does refrain from military actions that violate the laws of war, however "necessary" they might seem, and even when "the other side" is itself violating the laws of war. That's what makes "laws of war" meaningful in the first place: One side's violations do not justify, do not excuse, the other's.
Oh, that was too polite? Too cold, too cool, too intellectual? Well, then. Let's try some more-overt outrage:
It's pretty sad when you f*cking theocrats prove — yet again — that you can't f*cking learn anything. Not even from Northern f*cking Ireland, a context that should seem all too f*cking comfortable to you assholes. Or maybe you're taking hostages and killing children because you're too f*cking cowardly to attack someone who actually can fight back, too f*cking insecure to f*cking listen. Atrocities are not a sign of strength, or resolve — they're a sign of fear, of cowardice, of complete lack of confidence in your own f*cking capability to win playground battles except by being all manly and beating up your opponent's six-year-old sister. And this goes for all of you f*cking theocrats throughout, and beyond, the Levant: You're all f*cking guilty.
"Never Again" means everyone. It means nobody should fear violence, murder, cultural annihilation, or anything else on account of their faith (or lack thereof) — or that of their ancestors, especially when "faith" gets mixed with "ethnicity" and things become even more tribal. (Nor the converse: Nobody should expect to impose violence, murder, cultural annihilation, or anything else on those who are different.) If "Never Again" means anything less than everyone, it's just another sectarian slogan of precisely that kind Tommy Sands rejected in the embedded song. Just another step toward Minersville or Tulsa or Wounded Knee… or Kishinev or Hama or Amritsar or Srebenica… "Different" does not mean "enemy," let alone "must be destroyed."