Why the hell would the Alliance have agreed with his actions when Gilneas left precisely because Greymane didn't want to pay for the camps and would rather exterminate the entire race, contrarily to the wishes of everyone else? That's a (citation needed) moment to me. He was still Alliance but acting on his own, and nobody in the Horde seems to blame Stormwind or whatever other Alliance kingdom for his acts given that at the time Kul Tiras was already heavily isolated.
The Dalaran point I'll grant but seems a plot hole to me as later lore reveals that elves are also influential in Dalaran which also isn't the ruins depicted in WC3. I wouldn't even be surprised if Reforged changes this a bit.