I think its a bit too simplistic to just separate them into “the fel horde” and “the Horde of today”. Yes they are two different political entities however one evolved into the other. There are still Orcs alive who took part in the slaughter of draenei, and the actions of the first and second wars. To just park responsibility for that on the few at the top is a bit naive. If orcs were these truly noble spirits then could they not all have refused like the frost wolf did? You have to concede, for many regular, uncorrupted orcs who were following those who were corrupt, there was still some appeal in going to war and testing their might against new enemies.
The humans have been subjected to this on two occasions over two wars, you might forgive them for stereotyping orcs as a lot have a tendency to follow bad leaders and do what they say, irregardless of their own scruples. Let’s not forget this isn’t simply some orcs being rude or beating them up, we’re talking mass invasion and slaughter. I’m not sure many people would be concerned with labels like racist or xenophobe when the bulk of the species In question has demonstrated on two occasions how they’re more than happy to try to obliterate your own people. Even if it’s down to their leaders, it’s a risk you might not want to keep around in case another such leader surfaces (hi Garrosh)
Additionally even thralls new horde is not free of blame. Ashenvale was pilfered and plundered by thralls new horde. Night elves have since joined the alliance. Their first impression of orcs isn’t exactly a great one either.
I’m not suggesting that the alliance are perfect or “the good guys”. But there are reasons the alliance doesn’t like the orcish horde that extend way beyond a simplistic “OMG alliance racist much?”, despite what Mr blightcaller whispers in your ear.
Regarding tauren and trolls, trolls have a history of conflict with the alliance, particularly where they ally with orcs. It wouldn’t be remiss for the Alliance to assume that these new flavour of trolls whom have allied with orcs may be similar to the last lot. Its not as if to the outsider they appear too different in terms of how they fight, appear or behave.
Regarding tauren, that’s a trickier one. Without the Horde yeah the alliance have no good reason to dislike or attack tauren. That said these peaceful cow men seem intent on defending those orcs you have major beef with to their dying breath. Doesn’t exactly paint them in a good light to the alliance does it? Remember the average alliance Joe doesn’t know what we know. He doesn’t know that the tauren have a noble spiritualism and history with night elves. What he sees is a gigantic cow man swinging a mace at him because he was trying to attack an orcish Grunt.thats probably enough for him to go “these things are dangerous and want us dead as well”.
The only race in the alliance to date who actually wants them wiped off the face of azeroth is the Light forged Draenei, as evidenced by their various texts in the incursions and when doing the hordeside pre Bod where they mention how the Horde need to be purged because they are wicked. Most other races don’t signal such a desire, rather they want the Horde disempowered so it’s no longer a second superpower and no threat to them. Once they are dismantled I just don’t see Anduin issuing a slaughter order on all the orcs tauren and trolls etc. Rather it’d be akin to giving them all a “regime change” to ensure they never grow into a power again.
After all Anduin has made it clear, he wants Sylvanas first and foremost. Nobody else has made it clear they wanna go further (we may have to ask Tyrande post vengeance) and wipe the Horde from existence.
The war for the Alliance is about what it’s always been about, neutering threats to their own existence and keeping them in check. The whole “orcs in camps” should make it clear that they’re more about this stance than just killing them all “because they’re different”.