Odyn self-aggrandizes. He's an unreliable narrator. You're supposed to read between the lines, which is -why- you get the clues like the author saying things like "Others say it happened differently, but why believe them when Odyn will tell you, himself?"
There isn't any proof that those orcs -were- Sha infected. And the witness to the crime (Rell Nightwind) stated that he thought they were trying to surrender. But even if they -weren't- surrendering, they were unarmed and helpless because they were swimming. Killing them, there, was a war crime. As in geneva convention war crime.
And I'm not trying to say that the Alliance are "Clearly the Villains" or that they're "Worse than the Horde". I'm saying that they commit crimes and then people ignore those crimes because it doesn't fit their personal narrative of "Alliance Good, Horde Evil"
Still waiting for you to tell me which of the crimes I listed weren't crimes at all.