Originally Posted by
Super Dickmann
As regards Lordaeron it's fairly obvious that the fact that they were caught too far forward, that these blightthrowers were there from the very beginning and that none of them take issue with the gassing themselves makes it plain that it was just part of the defensive plan and that they were not meant to be there in the first place. If anything should have been a huge taboo there, that would be the necromancy, which goes against tauren and orcish customs to a massive degree. Using poisons or Blight by itself is something even the Cenarion Circle do at one point, so it doesn't carry the same connotations, not to mention the whole bit about its initial use being by apparent traitors. We'll sidestep the whole Wrathgate nonsense entirely.
But where it does concern undeath, I agree with you that it should be a much bigger deal and it should be a greater ground for mistrust. There's been an overall softening of attitudes towards all sorts of evil things, going from Forsaken being kill on sight in Vanilla, to the mopeathon of BTS and from warlocks hiding in the basement or getting the noose to Varian loudly praising people who suck out souls and use them as fuel to summon demons from hell.
That having been said, this was not an entirely hostile relationship at any point. In Cataclysm we see cooperation and mutual support with things like the seadogs, Orkus and especially Cromush's gradual turn from minder to honorary Forsaken and we are told that Sylvanas has taken ample credit for the victory over the Legion, saving the Horde at the Broken Shore which was only possible through her val'kyr, moving to Orgrimmar and pandering to all their cultural customs and attending events. She has purposefully aimed to soften the Forsaken image. On top of that, of the wars waged, only two areas are actually using heavily Forsaken tactics - Darkshore, where there's no one else to see except a bunch of goblins and Lordaeron, where it's their home so it's something of a given. So there's reasons set up within the narrative for the attitude to shift, though it should be nowheren near as drastic, nor tolerate things like said necromancy of their own that go heavily against the belief system of many present.
Garrosh was extremely popular precisely because of his victories over both the Scourge and the Alliance among the common folk and the army, which is basically the same thing for a lot of the Horde races at the end of Wrath, per Shattering. He maintains this popularity among the races even up to the end of Tides of War when he's already tightened his grip on the Horde with a giant parade present where all the races cheer him on, and we're shown his charisma among the tauren, Forsaken and orcs. Only the heightening of racial conflict and his heavier approach explain the mass turn against him by the end, not that people really wanted to be friends with the Alliance or regretted the amount of territory or technological progress he brought them, what with even Vol'jin preferring the Divine Bell go to Garrosh after his assassination, than to the Alliance.
The people who whinged about Garrosh are the same cabal of dickless wonders and their progeny that are bitching now, disregarding Vol'jin since he's a ghost. Cairne committing suicide over a false flag and Baine then banishing his own people are just the same as what Baine is doing now, with again zero impact on the attitudes of his people, who were alright with self-defense or even an aggressive war then and now. Vol'jin speaking the troll case against war is different when there's Kul Tiras involved, they're even fewer than they were before and the Warchief in charge is Vol'jin's own pick. Bob is Bob. Couple that with Sylvanas' more subtle approach towards controlling the Horde, her pandering to their customs and apathy to what they do provided they contribute to the war and a bit of spin, it's easy to see why people don't hold ejecting one of their long-term foes from the continent against her. The Horde have never been pro-peace, they've always been a warlike group and they've never in their majority wanted peace with the Alliance on poor terms.