You get in to a sticky morale quandry when you call battelfield deaths murder. Casualties is a much better word, because let's face it, both combatants are trying to kill the other. Still, it's just a word so probably not worth arguing over.
I dislike the references to the Scourge. Yes, they are raising others into Undeath. Tasteless, to be sure. But they still do offer a choice. Serve the Dark Lady or be returned to death. The Scourge had no-such quandries about forcing someone to serve.
I don't even know if you could claim they are offering a "Serve or Die" option because technically it's like waking someone up then putting them back to sleep if they offer... It probably is though, I would wager I am being a bit more forgiving because I tend to try and not view the Warcraft world with my Real Life morales.
Technically, war is murder. Literally. You are doing your best to kill the enemy's soldiers. It's just justified because it's attacking/defensive against soldiers. It gets sticky when civilians are killed, but by the broad technical terms of murder/killing, soldiers are mass murders.
There's a reason people are saying in the forums and in game, the Forsaken are like the Scourge. They are using many of the same tactics (blight/plague. Val'kry, raising more undead..) Even Garrosh, for all of his blundering, states there is little difference between the Forsaken and the Scourge now. The Forsaken are called Scourge because they basically are a lite version of the Scourge now. If Sylvanas could figure out how to kill Bolovar and take the Helm of Domination for herself, she'd do it in a second.