Yes, I know, but they present it as "bad", and Rell even says it was wrong. It was his doubt in the action that almost allowed the Sha of Doubt to possess him. The same scene on the Horde, Nazgrim almost gets possessed just because he doubts his mission after losing the Horde airship, thinking Garrosh was going to kill him, not because of any "wrongs" committed when he slaughtered the entire Alliance base and straight up said "We have no room for prisoners. Don't let them run away." when he sends you into the fray. That is the problem, they present the Alliance as having a conscious about the bad stuff they do through some of their character, while they present the Horde reveling in it, or shrugging it off.
On the Alliance side you feel welcomed into the Pandaren village for helping them. On the Horde side you feel like freeloaders just because the natives are too nice to kick you out.
Speaking of airships. Man do I feel bad for the Horde when it comes to airships. The only airship that has been able to survive is Orgrim's Hammer in Icecrown (and even that is dubious, considering playing Alliance causes you to shoot it down in the ICC raid). Send one to take over Gilneas? Crashed by the Worgen. Send one into Deepholme? Shot down by the Twilight's Hammer who took over the Alliance airship. Send another new one to fight at the battle of Wyrmrest Temple? Deathwing decides to body smash it into oblivion. Nazgrim takes yet another "brand new" airship to claim Pandaria? Kaboom after the first six quests.
And yet on the Alliance side, they treat the Skyfire like a flying death fortress and aircraft carrier. It survives and you keep using it to obliterate any Horde in the region using flares to call in fighter squadrons. I know it has some sentimental value, being the airship that chased down Deathwing during the hour of twilight, but come on, we can at least throw the Horde a bone in the airship category!
What? Trolls have never been "mercenary" in their alliance with the Horde. Vol'jin credits the Horde with saving his people and is loyal to the bone, so much that he turned down joining the Zandalari, saying "The Horde is our family now". He hates Garrosh, but still stays because he still believes in what Thrall's Horde stood for, and wants to see it returned to that.
While Sylvanas and Gallywix are in it for very selfish reasons, Vol'jin, Baine, and even Lor'thremar are presented as staying purely out of loyalty to what they believe the Horde should stand for, back like it was under Thrall.