The arguments I see against it usually boil down to:
a.) "There's no Asia or Africa in WoW!"
Which, yeah, but point to Europe on Azeroth, Draenor, Argus, or any other realm of existence. Before anyone says that all human nations are European - see my next points about Kul Tiras and Asian men that have been in the game since Vanilla.
b.) "I'm sick of companies giving in to SJW
DEMANDS!"
I never really saw anyone
demand for this to be added - it's just something Blizzard decided to do. It just gives players the options to play as themselves more than just caricatures of African/Caribbean cultures (Trolls) or caricatures of Asian cultures (Pandaren). It's just a nice thing. The sky isn't falling, you don't have to play as these skin tones/face shapes if you don't want to. I absolutely love the way they look, and I might make another human, personally.
c.) "There's no lore to support this! It's coming out of nowhere!"
Similar to the first argument, but distinct still. Well, there have been black people in novels, like
Makasa Flintwill in
Traveler, who is from Stranglethorn. Kul Tirans have had a couple dark skin tones since the start of BfA with no additional lore - they just can be black. An example of this is
Dorian Atwater, the shipwright for Anduin's Kul Tiran ship. There were also people like
Woo Ping,
Wu Shen, and
Shen Kang Cheng that were meant to be Asian - they even had Asian eye shapes from Vanilla-WoD, until the model remakes.
Besides all of that, evolution in WoW's lore isn't at all like it is in the real world. There are things like the Curse of Flesh, the Cradles of Life (like the Vale), and even magical artifacts that have evolved people different ways. Humans themselves are a product of the flesh-cursed Vrykul, who were once made of metal - that means that there isn't a reason at all in WoW for real world evolution explanations. There also doesn't need to be an explanation for why some humans have "Pandaren names" - some of the Mechagnomes have Asian-inspired names as well, and we
know they never interacted with Pandaren before.
So, in the end, it has nothing to do with lore, just the real world humans that play it, as stated in the first point. Fact is, it's happening, so you may want to get used to that fact rather than lose sleep over it.