The player in my group who plays the Missionary is sort of shy, but he really likes the fluff behind the Missionary class and the Ecclesiarchy in general. His character is rather hateful of xenos, and our Rogue Trader just recently hired four Kroot as mercenaries on Footfall (we're playing Lure of the Expanse). The Missionary is upset about this, but I don't think he really knows how to roleplay this in a fun, effective way.
My first thought would be for him to either flip out and just flame them all (with the help of his underlings). But I also had the idea of the Missionary threatening to lower crew morale (well within his power to do so) if the Rogue Trader doesn't dump these xenos scum ASAP.
What do you think? I'd love to pass along a suggestion or two for him to choose from.