This can be true for instance Drizzit's anti racist metaphor falls flat because 99.9% of Drow really are vile bastards. The idea of evil species isn't actually racist as theirs an utterly huge difference between people with a diffren't skin tone and an entirely diffren't species from humans, with a diffren't psychology. However seeing as people have taken too using fantasy races as a metaphor for real life race relations(which I honestly hate, stop dragging real world issues into fantasy worlds, that's were I go too escape this stupid world) I guess I see what your saying about racist conations with evil races. However almost all "evil" humanoid monsters are playable and can be whatever alignment you choose (alignments in the book are more suggestion then anything else really, and alignments are stupid too began with and everyone). However I see absolutly no issue with making chromatic dragons, beholders, mindflayers and the like, evil by their very nature.