It’s just an incredibly strange and annoying narrative to take. The current Horde, the citizens, have very, very little reason to be supporting such a massive and wanton slaughter that happened at Teldrassil. And if they do their reasons must be incredibly petty.
In a logical universe, people who live their lives in war generally don’t want there to be more war unless their backs are too the wall or something super egregious has been done to them personally. The only things the Alliance have done to the Horde were in retaliation/defense, or were spying measures. If Sylvanas has the support of the vast majority of the citizens of the Horde, then the following has to be true:
Orcs: A race that supposedly prides itself in honor, in victory or death, are fine with the use of Blight in battle, and the slaughter of hundreds of civilians without allowing them the chance to fight back.
Tauren: Fine with the burning of a World Tree and using azerite, the blood of the Earthmother, to make weapons. Also the attacks on the night elves, the very people who re-taught them druidism and brought them on the Cenarion Circle.
Trolls: Wanton raising of the dead in flagrant violation of Bwonsamdi’s own ways. Also the slaughter of the elves who also brought them on to the Cenarion Circle.
Blood Elves: Had the draenei literally save their race, draenei who are part of the Alliance. To say nothing of the Scourge attacks being little over a decade ago, and now the exact same thing is being done to the night elves. But this is fine.
Nightborne: Do I even need to say?
Pandaren: Don’t need to say.
Goblins: Get a pass, they’ve always been this way.
Forsaken: Are fine with this apparent Scourge-like behavior.
If this is the case, what the hell can Thrall and co. even do? The Horde members are either total warmongers for the sake of it or they’re the dumbest and most easily led collective alive.