1) Episode 7 Stormtroopers probably aren't clones of Jango Fett any longer, there might be some of the 501st or other original legions, but most of them are local militia forces. As you can read later Palpatine hated aliens, but he never showed any dislike of different humans, I mean how could he, he was grey. I don't know about you but I don't know many grey humans. (http://upload.wikimedia.org/wikipedia/en/8/8f/Emperor_RotJ.png)
2) I still have a small problem with his character, and it isn't his skin color. He doesn't fit what a soldier should be, he looked more like someone freaking out on some kind of drug, not a professional soldier. Give him a proper weapon and put him in a lineup with other Stormtroopers, standing up straight and whatnot and he'd probably look fine, though the entire point of the Stormtrooper armor is to make it look faceless fearless army. Which is kind of broken when you see a stormtrooper freaking out in the desert.
3) Previous posters are correct, during the Emperor's reign he was extremely xenophobic, although he was from Naboo, he really disliked anything that wasn't human, non-humans were traditionally barred from positions of power, and while most of the EU lore isn't in use anymore it is still there, and the Emperor despite his prejudices would give people who did a good job, power, like Admiral Thrawn, (http://www.starwars.com/news/the-legendary-star-wars-expanded-universe-turns-a-new-page)
Off-topic - Lightsabers with Crossguards have been in the lore since 2004, they were from EU Comics and Pen-and-Paper Star Wars games. And the Sith is wearing a Mandalorian Mask, to those who aren't familiar with Mandalorians, Jango and Boba Fett (And by extension the clones) were Mandalorians, if they were true Mandalorians or just adopted their culture is unclear. (http://starwars.wikia.com/wiki/Crossguard_lightsaber)
Further Off-Topic and an Edit - There is a theory going around that the Sith is Revan, for those not aware, Canon Revan was a woman.