Hussar
Legend
To be fair, Eberron also has the irredeemable evil types you don't have to worry when you put them to the sword. The Emerald Claw is to Eberron what the Nazis are to Indiana Jones. If the Quori, Daelkyr or Lords of Dust are involved, there's no question of their evil. The Aurum literally are Bond Villains.
Eberron's a bit of an odd duck to be honest. It really depends on how you want to frame your campaign. If you want the noir aspect to come out, I think you really have to avoid some of the more wahoo elements of Eberron - the Daelkyr and the Quori for example. The Dungeon adventures set in Sharn about the serial murderer (and I forget the names of the adventures) work very well for a more noir feel.
OTOH, doing straight up D&D in Eberron is very easy as well. The one campaign I played in Eberron didn't see too much in the way of moral relativism at all. The bad guys were bad guys and needed killing/stopping.
I suppose any campaign setting can be framed in a similar way. Greyhawk can certainly be seen as a morally relative landscape, or a very traditional one. It all comes down to how you frame the campaign, rather than the entire setting.