Without turning this into a big metaphysical or moral debate I just want to state for the purpose of the your mindset as you continue to read is that Evil is relative. Simple as that.
A common practice (and GM Belief) is that certain races are bad, evil, or to monstrous to be a part of the party. This trope is common with fantasy games but bleeds over into other genres as well (I will focus on the fantasy genre). The prominent examples that spring to mind are the Orcs, Goblins, and Dark Elves. I can blame the literature of Tolkien (and the writings that have followed in his footsteps) and blame the stagnant writings of TSR for the Dark Elves.
I understand the need for adversies and the like but why are all orcs inherently evil (unless it serves a specific campiagn purpose)? These things are considered evil across the board for no other reasons then that is the way it has always been done.
I cannot can't the times that I have had an awesome character concept but that concept was shot down becuase of the race or in rarer circumstances becuase the rules in question handicapped the said race to much. I remember that I had this great idea for a Ratkin pirate for a pathfinder game but the GM said people will think your shaven and all. How hard would it have been to hand wave it and give me a penalty on social interactions and through some difficult social interactions my way becuase I was a Ratkin? What's really baffling is that Tieflings are considered a standard staple now and have been for sometime but other races are still bad...
This brings me to the point of Necromancers* and undead. I have always had a habit of thinking outside of the box when it comes to characters and have circled the ideas of Necromancers and playing undead in some form or another. Both of these suffer from the usual evil for evils sake trap but there is so much grey in that area that it can be easily done. Another problem is that most rules do not have offerings for Necromancers (if they do they fall flat either mechanically or thematically though some of the decent examples have been the True Necrmance, The Animator, and the Pale Master but even these take some serious heavy investment with diminishing returns) or undead (outside of powerful intelligent undead - though Eberron had a stroke of genius with their positive energy powered undead culture). I think if the dialog between the GM and the player is there having a PC necromancer or undead of some from can be really rewarding. I remember I great game I played in where one of the players was allowed to play a necromancer (he hailed from some nation that necromancer was the norm and honestly didnt see anything evil with it and let me tell you, he played that to a t) and it was a blast. It really made the whole campiagn more memorable and the role play that came out of certain situations was off the charts. I remember one time after we killed an ogre he resurrected it as a zombie and it followed us around and it was all good until we had to go to town and the townspeople would not take kindly to an zombie ogre shambling around. So, our resident necromancer tied it to a tree and throwing some blankets over it and we retrieved the zombie ogre later.
My whole point with this is that I urge all GMs to start thinking outside of the box when it comes to the more exotic character concepts, races, and their interactions with society. If some race is going to be evil or some concept/race isn't acceptable then have a good role play or setting reason in stead of the usual mentality of that is the way it has always been. When in doubt, ask yourself why are orcs inherently evil?
As for players, I challenge you to do the same thing with your characters. Think outside the box and use the system and setting (with GM help as needed) to fit your concept, not the other way around.
*Disclaimer: My ideas and theories about Necromancers/nature of undead have been strongly influenced by the Diablo II/Diablo III games, Death Knights of Dragonlance fame, metaphysics, the Scarred Lands supplement Hollowfaust: City of Necromancers, the nation of Geb from the Pathfinder cosmos, the Deathless and their society from the Eberron setting, The Curst from from Forgotten Realms, the Baelnorn Lich from Forgotten Realms, Mary Shelly's Frankenstein, Washington Irvine's The Legend of Sleeping Hollow, of course the comic and movie The Crow, the ghost concept/mechanics from White Hack 2nd Edition, and Wraith: The Oblivion.