"Orcs," in LOTR (the book) were not a race of beings equivalent to Hobbits, Elves, et al, with their own civilization, culture, and society. They were constructs of Sauron; whether by mutating/hybridization or just magic isn't entirely clear. Saruman gets into the act by "creating" the larger, more aggressive (!) Uruk-hai in some similar Frankensteinian manner. The point is that Orcs didn't just happen to be some other bunch who saw things differently. They were created specifically to do the Evil One's bidding with no will of their own.