Illidari, at least within the Alliance, seem to be free to kill should they seem like they lose control. I think this says a lot about the attitude Anduin and the others might have. It’s tolerance. Barely.
You may establish a camp in the Mage Quarter. The Alliance will have need of your skills if we are to face the Legion.
Make no mistake though. Should your kind give in to the fel energies you toy with, we will treat you like the demons you are becoming.
It’s also interesting what Varian thought about the blood elves alone during Wolfheart. You can imagine then, what he might / others might think about demon hunters:
The orcs aside—and they were also among those of whom Varian was suspicious—the king could not see any reason to believe in the honor of blood elves—high elves who had turned to absorbing demonic magic after the loss of their vaunted power source, the Sunwell, and had subsequently become addicted to the fel energies.
At the same time, the Horde has a deeper focus on loyalty than the nasty magic they employ, though Saurfang has a bunch of stuff to say about that. However, Sylvanas only cares about their absolute loyalty. This might be a fairly important aspect between the acceptance of blood elf demon hunters within the Horde:
Tell your Illidari within Orgrimmar to make ready to serve the Horde.
But make no mistake, your kind once served the Betrayer. Betray me, and there is no world you can run to that will save you from my vengeance.
I personally think this is an extremely overrated point for several reasons:
A. It is unlikely every civilian on Azeroth read the WoWpedia page and knows what transpired at the Seat of the Pantheon. In fact, I can’t remember a single line by any NPC even ever mentioning it.
B. Illidan’s plan to open a rift to Argus brought victory in the end, but at the price of many lives on Azeroth. When you are on Argus, you can see how many Legion ships seem to be encroaching on Azeroth as a consequence of bringing the demon home world in spitting range of Azeroth. There’s a reason Khadgar and everyone else is absolutely horrified when he does it at the conclusion of the Tomb of Sargeras Raid.
C. Illidari have sadly, and that might just be Blizzard’s poor depiction of it in-game, not done that much more than other order halls to defeat the Legion -during- Legion.
D. The razing of Nendis and other crimes the Illidari as a faction have committed are unlikely to be forgotten.
I think this is the most realistic of views and in line with what see from dialogue swithin the Vault of the Wardens and everywhere else (for example the Kirin Tor jailor in Dalaran).
it is extremely curious to see so many demon hunters be openly accepted in towns or even the forests of Ashenvale with glowy armor and weapons infused with fel magic. Especially druids would be outraged, I imagine, as nature itself seems to react fearful and disconcerted towards -arcane magic- let alone fel magic. I will seek out the quote in question tomorrow. I believe it was in Stormrage?
In any case, they are scaled, fel-infested abominations with a literal demon bound to them. It will make the average character not only suspicious, but also constantly remind them of the Legion that once took their loved ones and their home. They will scare the children in towns and cities with their horrific sight.
In addition, they are using a magic that explicitly feeds on life. I just don’t see them being anything more than tolerated, and I also don’t see why an Illidari / demon hunter would ever bother his own people with his vile presence without a good pragmatic OR psychological reason.
There’s a reason they have their own little corner in the capitals. Their own little bases out in the world. Their own little floating island outside of Dalaran. Very few want anything to do with them and never will. That’s just how it is reflected in-game, and what logic seems to dictate.
One last thing:
I feel to a large degree, RPers have just been desensitised to the presence of warlocks, undead, void elves and demon hunters within the faction (fairly small populations in the grand scheme in lore, but quite widespread in RP) and are thus much more accepting than they should be. In addition, people don’t like to exclude others from RP. I’ve met many who didn’t wish to kick demon hunters out to not isolate them from roleplay.