And what of those actions has Garrosh himself ever personally suffered? While stuff like that was going on, he was either A) Not born yet B) Being a scrub orcling that everyone laughed at, or C) an emo chief who everyone was getting fed up with. Varian, however, saw his father murdered by a half-orc assassin, witnessed his home city burned to the ground by the Horde, and was enslaved by orcs for a time.
Garrosh's reasons for hating the Alliance is little more than him seeing them as a rival to be swept away so he can claim the glory prize. Chynn? Yeah, I may think he's a douche but he does have good reason to be so upset.
And I'm sticking up for him? Wonders never cease. 0_o