You're just making an artificial line. Much like at one time people from eastern Europe were not considered "white", or how Irish immigrants were discriminated against. Then the line changed and Irish and Slavs were considered "white" and "good".
I don't have a problem with evil orcs or evil fiends in my campaigns. But I think any line we draw between them is completely arbitrary and just as valid a topic as any discussion of racism in D&D. That's why I continue to repeat that we should just make it clearer that alignment is just a default, do what makes sense for your campaign.
There's always an artificial line. That's how this works. All I want in D&D is for someone to tell me where the artificial line is. I wanna kill bad guys and take their stuff.
These bad guys are too Irish? Sure, change them, move the line, do what you have to do. These bad guys are too black? Too white? Too Christian? Too Muslim? Too Asian? Fine. I'll change whatever I need to in the game to make it not offensive. But at the end of the day I need the line. I just want to play a game without worrying about the moral quandary of what happens to the mother and children of every mook and monster.