First of all, let’s not forget that the original Horde of Warcraft I & II were the puppets of the warlock class and the Burning Legion, and that they were driven to do a lot of those things by bloodlust and by their monstrous leaders at the time.
Let’s also not forget that the orcs were also punished with internment in camps across the continent, supposedly with the intention of ridding them of their bloodlust, but for some reason these camps weren’t dismantled that goal had been achieved. With no foreseeable end to the Alliance Internment Act under the rule of King Terenas, that scenario would have likely ended with the death of an entire people.
When the Horde was reborn, it was a new Horde with a new ruler free from demonic bloodlust, a new political entity that could give its constituent peoples a second chance. While this Horde is guilty of some degree of colonialism, there’s no sign of the centaur or quillboar ever trying to peacefully coexist with the Horde, they tried to kill them as soon as they arrived on the shores of Durotar and stepped into the Barrens. It was kill or be killed.
As for the matter of not belonging on Azeroth at all, it’s not like they could go back to Draenor at all, which had been wrecked by a megalomaniacal leader of their people. You could shrug and say that this was their fault, but I could also point out that the fall of Stromgarde happened primarily because of Galen’s actions. He killed his own father, who was a much better king who held the nation together. Under Galen’s rule, the whole thing crumbled. If all orcs in their entirety are to blame for the actions of Ner’zhul, then all of Stromgarde is to blame for the actions of Galen.
But the most important thing I have to say about all of this is that it is wrong to expect any race or species to peacefully accept their fate and fade away into oblivion, no matter what their past crimes might have been. They are going to want to live and they are going to need homes if they’re going to accomplish that.
Underneath Thrall, in order to avoid conflict with the Alliance, they found these homes almost exclusively in the barren and undesirable corners of the world, and in the lawless places where the Alliance were incapable of keeping the peace, such as the Arathi Highlands when World of Warcraft first came out.
Their settling of Hammerfall and Go’Shek Farm was more or less built on the fact that there was no one there to stop them, these places weren’t taken from the Alliance by force as far as we know, as the narrative from Stromgarde focuses on it falling due to the actions of the Boulderfist Ogres and the Syndicate. Besides, by the time that Stromgarde was reclaimed and the dominant force in the region again, the Horde had already lived there for long enough to feasibly build their own homes and own families. Is it really right to then kick them out?
The vast majority of the population fled south with only the proud military elite remaining behind in Refuge Pointe and an isolated enclave in Stromgarde, and even they left Hammerfall and Go’Shek Farm, which would’ve been occupied and used as bases of operation by the Syndicate, Boulderfist, Witherbark and other elements if it wasn’t for the Horde claiming them.
And while there might have been conflict between the Horde and the Alliance in the region at the past, both factions have shown that they want to pursue coexistence at this point and the Horde are happy to limit themselves to the territory that they previously settled in the absence of the original inhabitants - an old internment camp and a farm to keep its population fed. It’s not like they’re asking the Stromic to share the streets of Stromgarde with them.
The relatively recent arrival of the Mag’har in the area complicates things, but the issue remains the same - it’s not like they can go back to alternate Draenor to where they belong. Just like the green-skinned orcs, they require a home on Azeroth if they’re to survive. They shouldn’t be morally compelled or expected to move en masse to Outland’s Nagrand and wait for it to crumble beneath them and send their entire race into the Twisting Nether.
They want to exist and they need somewhere to live and one old internment camp, one farm and the hills that surround them isn’t a particularly big ask, especially when they have already belonged to the Horde for twenty years due to Stromgarde’s inability to maintain law, order and control over that part of the region.
