It seems evident enough that Bethesda intentionally made the Stormcloaks more racially biased compared to other groups; they even gave special race-specific dialogue to Stormcloak Guards that are more snippy and negative in tone towards your character's race.
http://uesp.net/wiki/Skyrim:Guard_Dialogue
Normal Guard: "What is it Khajiit?"
If Guard is a Stormcloak: "What do you want... cat?"
I don't want to be the one to ruin this peaceful discussion of the civil war, both sides of it were evidently meant to be gray, and this was one of the things Bethesda did to propose that.
And Bethesda did a great job on that, considering too many have warred through thousands of threads debating who's good and who's not... almost like an actual Civil war of Elder Scrolls fans.