Because he still cemented the night elf leaders' surrender, preventing Tyrande from getting in the way. He managed to follow his code of honor and still win. Perhaps not as easy a road to take, but an important one with what's going on.
It was such perfect timing releasing this now, when every horde player (who's not a sociopath/enjoys roleplaying a villain...) is not exactly feeling patriotic or wanting to defend the Undercity of all places.