Possibly. But we don't have Neanderthals anymore. We only have minimal differences between living humans that vanish in individual differences and can't be properly measured. So racism makes no sense. If we ever get genetic engeneering and variant humans going we might reconsider but as of now racism is just wrong.What gets really confusing is that the races seem to be seperate species and yet they can make viable hybird offspring. If they're different species its not like comparing you to another human with a slight difference in genetics that manifests as a skin colour, which is about as important as hair colour really. It's more like If neanderthals still walked the earth, would it be racist to acknowledge the actual differences between them and us that are more than skin colour?
As for D&D, there are not only half-elfs and half-orc, but also half-giants, half-vampires, half-ogres, half-dragons, half-celestials, half-fay and half-elementals. I would not be surprised if i can dig out half-skelletons and half-golems somewhere. The ability to create offspring is meaningless for categorisation in D&D. It never was a particularly serious game.