Originally Posted by
Nathanyel
That's where your fallacy lies, a benefit for the Horde does not have to be a loss for the Alliance. Thrall fought Humans to get the Orcs out of Lordaeron, but once they were free on Kalimdor, he worked with Jaina's fugitives and the NElves against the actual threat.
Saurfang was for the War of the Thorns, because it was intended as a short conflict that would bring about complete Horde control over Kalimdor, with hostages in Darnassus ensuring that the Alliance doesn't retaliate.
Sylvanas throws that away, for no good reason (to the other races of the Horde)
She acts 'crazy', provoking a long conflict whose only 'benefit' could be creating more corpses to raise.
Other than that, the Horde does not have a clear advantage in the war of BfA, unlike the War of the Thorns. So, it can be argued that this whole thing is not beneficial for the Horde, and ending it would be preferable, even if this meant saying "my bad" and signing a peace treaty (which, again, was kinda the point of the War of the Thorns, only that the Horde would've been in a more dominant position)
Acting to the interests of your people and the Horde itself means acting against the Warchief, so that's technically treason, but you didn't hear many players call Vol'jin a traitor during MoP.
However, I agree with the mentions that Baine's motivations are improperly explained, but that's story neglect, not a character flaw.