I can recall and there was a major lack of investigation and therefore right to speak or at least speak with authority. Deep Tolkien investigation is fucking hard. Like next guy down from Shakespeare as an academically accepted author to study. The orc stuff mostly exists in LOTR but his issues regarding the orcs with his creation myth and making basically a race of cannon fodder kinda sucked and came from goblins and whatnot from folklore which had their own issues that he struggled with mostly came from his letters and the things regarding the south and east being colonized by asshole numemoreans is a brief mention in part of the silmarillion which is tough enough to read buy greater detail requires seeking out less fleshed out notes and writings and piecing it together. Peter Jackson technically didn't have the rights to most of this stuff but it could have inspired a more vague reasoning for these guys joining sauron in the films. Tolkien was old as hell and British and I'm sure he had some degree of racism to him, but gotta say, from anything personal or fictional I've read, haven't really seen much. I'd say Jackson had a way more racist portrayal of the subject than Tolkien