No race should have alignment locking in any direction, because people are people and can do whatever they want. Our goodness or badness isn't determined by our genes.
But, people are who they are because of the society they grow up in and how people treat them. If humans treat goblins like shit because they're goblins, and a goblin turns into a big bad because they want to kill the humans that slaughtered their village, then that villain is interesting for reasons tied to their species.
"No villain in D&D is interesting for reasons tied to their species" sounds very dangerously close to "I'm race-blind" in terms of not acknowledging that different people have different struggles, and racism is often a huge part of those struggles.
I feel like:
"No villain in D&D is interesting for reasons tied to their species" sounds very dangerously close to "I'm race-blind" in terms of not acknowledging that different people have different struggles, and racism is often a huge part of those struggles.