Quote Originally Posted by Ionathus View Post
Right, and my argument is that we then run the risk of making them too human in behavior and appearance (displayed attributes that are proven by the narrative), while only making them completely unhuman in morality (informed attributes that might only amount to a paragraph of flavor text from the DM, or throwaway statements from NPCs). That's the danger: that we'll arrive at "this thing is always deadly and you need to kill it to survive, don't try to reason with it" without doing any work to identify what makes it irredeemable. Without any other reasons to go off of, the mind might start to associate "irredeemable evil" with skin color or certain cultural behaviors, and that's the danger I see.
Again, you're coming at this from the standpoint that objective morality is a thing that exists and can be measured. I understand in D&D it very much is, but I'd argue that it's one of the biggest flaws in D&D's design and a rather black and white and childish way to put the world together. Is the dragon "irredeemable evil" or is it a hungry superpredator that has the same biological need to eat that a human does and cares about as much that humans very much want to not be eaten as a human would that a cow very much does not want to be eaten. A goblin is a fictional monster no different than a dragon, it just happens to be smaller and roughly human shaped. Unless the indicated by the author of the specific universe, why would the automatic assumption that being roughly human-shaped makes a fictional monster the equivalent of a human. In the real world, gorillas, chimpanzees or any of the other great apes are bipedal, roughly human shaped, and even capable of learning and limited communication with humans, but we don't morally equate them with humans. The question shouldn't be "is this creature evil as defined by some sort of objective cosmic standard?" but "is this creature dangerous to me/my family/my community?" Being highly aggressive or territorial by nature or seeing humans as prey are enough for conflict to exist and there's no reason that traits that exist in real animals couldn't apply to fictional monsters. Whatever the author decides serves the plot best.

To give another example, one youtube channel I watch portrays goblins as mutated degenerate humans, the result of exposure to high levels of magical basically-radiation. Despite specifically being mutated humans, they're still aggressive opportunistic raiders who are individually weak, but always move and attack in large swarms. They have their own language, religion and even currency and are intelligent enough to communicate with humans - there's even an insane human scholar (who they do not realize is human due to his face being covered) living among them and they trade with bandits. They attack caravans and travelers, find torture entertaining and eat human flesh. Is this a cultural thing or is it just part of their nature as a result of the same mutation that made them what they are? Well, the channel doesn't elaborate on that and doesn't really have to. They goblins are a threat and in the end, that's what makes them relevant to the plot.

As a final point, if an audience/group of players can't distinguish between fictional monsters and real people to the point that they "start to associate "irredeemable evil" with skin color or certain cultural behaviors" that speaks far more about them than the author/DM. It requires the same sort of backwards "logic" people have used to blame metal music or video games for real world violence and such claims have been proven wrong time and time again.