Orcs and goblins and scary monsters—bad. Dwarves, elves, humans, and hobbits—good. It's as simple as that. The good guys are the good guys and the bad guys are the bad guys.
The Lord of the Rings has never presented much of a moral dilemma, which is probably why some nay-sayers tend to see these films as mere tales kids' movies (how dare they!).
While these movies are clearly awesome for all ages, it's true that The Fellowship of the Ring isn't an intellectual inquiry into the depths of human depravity. Nor is it in any way allegorical, as Tolkien constantly tried to remind people. Instead, the conflict in Fellowship is a simple battle of good vs. evil.
But how can you have a morally transparent movie and also have that movie about war? Isn't war always set in a moral gray area?
Well, the answer is simple; you just use an age-old propaganda technique and dehumanize the bad guys. The orcs are humanoid, sure, but they are most certainly not human. They appear brainless, following orders with no volition of their own. They're sort of like a hive of angry bees. This is underscored by the fact that we rarely see single orcs, only masses of them in crowd scenes that effectively remove any individuality. In a way, they are more a force of nature than they are fully dimensional people; scores of extras for our heroes to fight against.