Considering the Draenei have been hunted for millenia, to near extermination by different races, and now individuals which are the antithesis of their very nature are welcomed, I can only see racism being an acceptable form for many Draenei to deal with this. Polemus will not be reactive, but active in his discriminations, due to the history of his people.
This is the same for almost all races, which have all suffered in some way from other racial conflicts.
Also in the Velen shortstory humans and draenei have a xenophobic exchange and nearly end up killing one another at the Azuremyst Isles.
Stop hating me! 
I make a dragon age slur at u.
I guess because the person had papers stating they can be in Stormwind 
Epic Permit RP trumps the predefined status quo of the setting!
Start calling all human rpers you meet âShemlenâ
nif eer elf bad
Void is an abomination as proven by Lord Stormsong and his corrupted tidesages, simple as. Death to all practicioners of the Void.
Anything can be an RP concept so calling it an RP concept adds very little
My character concept could be that Iâm Anduin Wrynnâs more powerful older brother but that doesnât mean itâs setting appropriate
The 1x (one) blood elf that hangs around in Stormwind in Valeera Sanguinar and that is an exception rather than a rule (given especially that AFAIK blood elves are more of a political affiliation than a distinct race)
Yeah generally that will happen until Blizzard decides to write the Horde vs Alliance dynamic out of this video game
In the years to follow, Antiles J. Hawk became for all intents and purposes; a pirate but not out of greed but for the desire to learn the truth.
I guess itâs an easy mistake to make
Are you actually advocating for the old trope of warlock licenses but this time Horde licenses?
That is absolutely epic but I also think it might be lower order RP that belongs back in 2009 so for that reason Iâm afraid Iâm out
Show me your Saurfang Supporter license please, or you will be thrown out of Orgrimmar. (Post rebel rp)
Whhhuuuur knif eeeere
I donât have to because Baine will personally tell you off 
I also have no idea, to be fair.
As the OP said, racism has always been a driving factor in the Warcraft universe. Garithos was an extreme and very direct case of racism, of course. Not every human will really hate a High Elf as much as he did. Most donât, but itâs up to the roleplayer to decide what his character thinks of them.
But the wars waged on Azeroth were mostly founded on racism (bar the wars where we fought cosmic forces and evil super-villains).
The very reason why the Horde exists is because itâs a product of racism, prejudice and exile. We, as the player, got to know that the Orcs drank demonic blood and became minions of the Legion. But did the humans during the First & Second War know this? Did the Draenei?
And what about the Forsaken? Their name even suggests that they were cast aside by those they called family once.
And if itâs not the Alliance hating the Horde (for racist reasons), then itâs, for example, trolls hating each other. Troll tribals do not get along with one another. Zandalari look down to them, âŚ
I never understood how people think that âracism is badâ in Warcraft, when itâs the driving factor of faction hatred and so on.
Perhaps itâs the homogenisation of races within a certain faction that led to this view. Nowadays, we just have so many different races in both factions that it might lead to the impression that everyone is now very tolerant and accepting (when that is barely even the case, especially if we look at the current state of the Sunreavers who were Sylvanas-loyalist to enact revenge against Jaina and the Alliance).
Especially with the main narrative after BfA, with Anduin coming into spotlight, trying to achieve peace between the two factions, a lot of people probably get the impression that the races are ânot so different after allâ and âbecause we banded together once, we can just cast aside the entire history of bloodshed and fight as brothers and sistersâ.
For the record I do believe that neutral RP and/or crossfaction RP can be done well as i have seen plenty of evidence of it during campaigns (e.g. cenarion guardians in Legacy of the Saurok, multiple tavern initiatives, infinite dark), but sadly more often than not it seems to these days degenerate very quickly into some seedy RP like in Booty bayâs case.
Setting is absolutely crucial and while I do believe you could make an interesting RP event around for example having non-horde member races briefly in Orgrimmar 9/10 times this isnât the case.
Someone get the Silverpain meme.
I think casting a shade of blue over your blood elf defectorâs eyes will make the concept redundant. Why not just roleplay a high elf instead?
People roleplay as a blood elf defector in the first place because they expect to be caught in this tension between members of the Alliance and themselves. I donât think a roleplayer creates a defector character without anticipating moments like that. They want to be recognised as a former member of the Horde, trying to some how and some way earn their keep, but I doubt they want to get killed instantlyâŚ
But hating on blood elf defectors or any defector is not really a bad thing in roleplay. The difference between them and the void elves is that we searched for the void elves to recruit them, which was planned between Alleria Windrunner and Anduin Wrynn. They were exiled from Silvermoon City in the first place so it was a good deal.
Meanwhile this sole individual who defected from the Horde begs the Alliance for sanctuary, receives a âpermitâ or w/e and the masses of the Alliance are expected to accept that this enemy is now a friend because they changed their mind? I always believe a void elf has it easy compared to blood elf defectors.
The true way to deal with the aftermath of a rebellion/civil war. Call for centric forgiveness and understanding & let everyone go about as they wish because âno further conflict must happen.â
I remember getting accused of being a racist ooc by some random player when my character called Carbek a cow lol.
Why wait for the aftermath? Epic radical centrist borderline OOC posting in the middle of a conflict is much more fun!
(itâs not actually donât do this youâre embarrassing)
I have to ask, did the rebellion/loyalist rp, especially the siege, have itâs own version of Neutral rpers during pvp-campaigns, that screamed at both sides to âStop, donât do this, think of the greater good!â ?