@Miko

So?
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If Varian thinks that he could easily extinguish the Horde *now*, he's dead wrong. So even with a survivalist attitude, preemptive and/or offensive war would be stupid. Moreover, surivalism isn't what is "right" it's only what is "necessary" if you believe it to be "necessary" for a certain cause. Otherwise, "right" is meaningless.
We know that the Horde isn't really alien in the sense that you describe. Orcs can even mate with Draenei and Humans; Tauren, Trolls and Blood Elves have been around before Humans; the Forsaken are Humans; and the naaru approve of the Horde. Varian should understand this by now, otherwise he's deaf and blind along with being stupid.
The truth is that if Varian was informed perfectly as to what the New Horde was like, he'd be "wrong" to want to war with them; instead, he'd build up defenses only to safeguard accidents from happening or extremists from attacking.
Varian isn't perfectly informed, but he should have enough information by now to do what is right for his people, which is to make demands of Thrall to keep the Horde in line and fight back if provoked, not to antagonize and be the aggressor. He's not too bad right now, but he isn't being at all smart.