["Because" is basically the long and short of it. Orcs and humans have been warring for a generation. Some of the ones freed from the internment camps still want revenge. Hellscream's people never saw the end of a whip, but they were wild and angry and slaughtered as they pleased without Thrall's guidance.

... It's a mess, politically.

He grabs his knife and cuts open the shank. Not quite done. Back into the fire it goes.]

I do not claim to know what he was thinking. Jaina told me that he was blinded by his hatred of the orcs. He had fought in the Second War and lost his own son to them. Jaina was able to set her pain aside for the sake of everyone involved, but Daelin Proudmoore would not.

Some people refuse to change. They cling to their pride and their hatred until their dying breath.

[His shoulders hunch slightly, and he closes his eyes.]

So it goes.