Assange putting "murder" in the title doesn't actually make it illegal homocide. That's not how any legal system works.
IMHO that incident is unfortunate because some of those people were innocent, and it is legally questionable, but there's also a strong argument that it was legal. A very far cry from exposing something clearly illegal like the My Lai Massacre or Abu Ghraib torture.
So all he's done is expose one legally questionable incident from 2007 by a single military unit during the Iraq war? I suppose I'm not forgetting anything then.