If we want to go by personal experiences, then here's one for you.
There was a particular Horde player on the server where I was at the time who liked to greif a particular set of Alliance quest NPCs. He'd flag PvP, attack them and then use epxloits to LOS the guard NPCs as well as anyone else who showed up to stop him. And he'd do this for hours on end, days at a time, killing the NPCs as soon as they re-spawned, then running away before he could face the concequences. The result was that, while he was present, the Alliance couldn't efectively quest in that area. They'd have, at best, a window of a few seconds between when the NPCs re-spawned and when he attacked him.
This went on for ages, until enough weight of complaints were handed in that the realm's GMs were forced to take direct action. They issued the guy with a string of warnings, and that didn't stop him. He then wound up with a two-week ban as a result. Once it was elapsed? He went straight back to it. Pretty soon, he was out for another two weeks, and then another as he continued to grief the same NPCs. He took to changing his behaviour when people showed up, going off the corpse-camp quest mobs to ensure that Alliance players couldn't tag them and finish quests; often he'd sit on top of them while flagged as to encourage Alliance players to accidentally attack him and get themselves killed.
And the Horde Community's response? They loved it. They treated this guy as a hero and encouraged him to keep doing it. Was it greifing? Yes. Was it immature and petty? Probably. Was it ruining the enjoyment of the game for Alliance players? Definitely. Was it considered an offence by Blizzards GMs? Well, the guy got three months worth of bans for it, so that should tell you something.
Now I've never, ever heard of a story coming like that from the other side, of an Alliance player greifing a Horde NPC with that level of determination and receiving that level of community support as a result. So I'd hardly consider it that Horde players are "better" people in my experience.
Also Jin? Check your facts. Illidan betrayed his brother and his entire race. He's the bad guy in this, not Malfurion. Ilidan sided with the Burning Liegon in exhange for power (much like Gul'dan and so many other Orcs I could name); Malfurion was forced to imprison him for his actions. Ilidan's hardly the good guy by any stretch of the imagination.