As a side note, I'd like to point out that Morgoth did not create the dark races from scratch. The Silmarillion explains how he captured Elves, and over time, twisted and corrupted them into the race of Orcs. Presumably he created the Trolls and Dragons in a similar manner. Morgoth could not truly create anything: he'd been specifically denied the power of creation.
This also serves to explain the universal hatred of Elves for Orcs. It shows them what they can become, for the Orcs can only be what the Elves are also capable of.
Needless to say, I don't support the idea of racism connected to this. The story is fantasy, it's about black and white; good and evil. Sauron's minions are the Bad Guys. The protagonists are the Good Guys. You can't have an epic struggle of good vs. evil with Aragorn setting down Andúril every couple of seconds to have moral discussions about the Orcs he's killing.
"You know, maybe they just can't help themselves... and jeez, I wish we could stop all this fighting and just get along..." /barf