Urriak Uruk
Gaming is fun, and fun is for everyone
Why are evil A.I.s ok but evil organics aren't? Some versions of orcs (Warhammer) are arguably just as prefab as robots are
EDIT:
And what about beings with a collective consciousness (such as Tyranids, to use another warhammer example, or to a lesser extent D&D's modrons)? They should be expected to all think alike (unless cut off from the collective like rogue modrons or that one genestealer cult)
Interestingly enough, Star Wars sometimes uses droids as a proxy for racism. In that, there isn't a ton of animosity between the various races (with some notable exceptions like the Empire being human-first), but there is a ton of animosity against droids. There are even instances of "we don't serve droids here," which is a pretty clear reference to an era of the American South.
Anyway, IMO, having an entirely evil group of humanoids is ok as long as there can't be any similarities drawn to a real-life group of people. If you have gnolls for example that sounds like the dog-hyena-people they are and have essentially no culture apart from "Like to eat people," that's fine.