But it is perfectly possible for other worlds/campaign settings to have species, even humanoid ones, that do not have the same degree of moral freedom that humans have.[/QUOTE]
If you ask me, no, you should not have to "make it clear in my campaign that you can't kill goblins because they are goblins".
But I think it is fair to say that if random new players were sitting at the table with you, saying this out loud would be a very helpful thing. That is where we are; and it is best to acknowledge where we really are first, and work from there.
True. That certain creatures do not have the same kind of volition as Humans is perfectly plausible in a magical world. Being explicit about this is a good idea.But it is perfectly possible for other worlds/campaign settings to have species, even humanoid ones, that do not have the same degree of moral freedom that humans have.