E - Evil (or perceived to be evil) factions/races

Look at the races or factions in many games.  There are the good guys and the bad guys.  But... what makes the bad guys so bad?

In WoW you see the Horde shown in both lights.  As good guys and bad guys, depending on which faction you  belong to.  It has a very Beowulf/Grendel feel.  Who is right and who is wrong?  This is a very interesting way to pose the two factions.  The same came be said about the representation of the factions in SWToR.  The Republic is commonly revered as the good guys, while the Empire are the bad guys.  When you get into it, both factions suck.

I understand the need to have factions face off against each other, but to assume that the other is evil is silly.  Planetside housed THREE different factions and it was never assumed that one of them was evil.  They were all simply different and fighting over something.  Everyone was a human, so I guess that may have helped the story there.  So does being an Orc make your faction evil?  What about SWToR, how can most of the races be human, yet have so many issues with a faction being evil?  Maybe it has to do with the extended role playing available in SWToR and WoW.  Maybe it is just because they feel like they need something to fuel the conflict.  Planetside was a conflict all by itself.

With the new Planetside game getting ready to start testing I am looking forward to seeing it's take on this kind of thing.  The first one was able to avoid the good and bad, light and dark, Horde and Alliance issue.  I have hopes that maybe we can move away from this kind of thing in the future.  Or, maybe that we can take a note from Planetside and have more factions with more interests than just two warring factions.