Illusion of choice in full effect. You basically do the same thing you were going to do anyway, but Nathanos tells you you're just pretending to be against them. Also it's real nice that the Alliance are intervening in a Horde problem again. It doesn't feel very great that Saurfang and Baine are only allowed to stand against Sylvanas because the Alliance had to bail them out or leave the door open for them.
It always amazes me how passionate and virtrolic the #TeamSylvanas group gets. I don't remember Garrosh having NEARLY this much fanatical fanboyism.
Some of us are with sylvanas and want them dead.