[quote=@Zarkun]
Depends on how strong the anti-human sentiment is in the Scarlet Moons.
[/quote]

It's fairly prevalent in the lower ranks, since many recruits joined up due to the abuse from humanocentric Imperials. These guys were slaves, second-class citizens, underpaid laborers and the victims of many speciesist movements. About half of the Scarlet Moons flat out refuses to fight alongside Humans in battle, on the fear of getting shot in the back. Most higher ranking officers don't have problems with Humans, or are pragmatic enough to overlook their disdain. For the sake of any Human member's own safety (so they don't get lynched by vengeful non-Humans), they are only sent to fight if they have extensive combat experience and/or rare skills.