People used to be extremely racist, it was used as a tool by rulers to send people to war. You only need to look at some of the propoganda published by certain governments to realise that. I imagine the same would happen in the TES universe. Regardless of what guards should be they need to be realistic and representative of their culture. Guards don't even serve justice, just their Lord.
And I'm not sure how any of that is relevant to Skyrim. The King is dead. The land is at war between rebels and the Empire--neither are racially exclusive. The world is being threatened by dragons. The universe is at risk of ending. Where's the motivation for so many guards to be racist at a time like this?
and people don't want racism, just realism that will add that extra bit of depth to the game.
I wish I could believe that, but no, people are all torches-and-pitchforks about their racism. Just look at the hundreds of threads about Argonian-lovers wanting all Dunmer to die, and vice versa. Sure, it's just a fantasy game, sure, a bit of racism adds depth, but it certainly seems like many people are most excited about the chance of acting out pure racism. I just don't get it.
And? They still do. Welcome to reality. And I know I know, it's a game. However it's trying to represent a believable Universe that is shaped largely off our own. Guards should be just as likely as anyone else of harboring racial and other prejudices.
And how much individual personality have we seen in guards in the past games? Absolutely none. Maybe the head of the guard has a personality and things like that, but the rest of the guards are always just clones of the next. If we get to the day where it's reasonable to expect every single NPC, right down to generic guards and bandits, to have their own personality, then yeah, sure, but that's not going to happen with Skyrim. It's kind of an all-or-nothing thing, and I see no solid reason to include racism, no more than including a guards food preferences or sixual orientation. If the head of the guard is racist, maybe those guards could be a little less favorable of certain races, but a guard-by-guard basis is not realistic.