Thanks for the responses, but judging from some of them, I think should have been much clearer in my initial post. I'm not complaining about the presence of mixed CSM/human parties in BC, nor am I asking for a tutorial on how to run a game without the players attacking or bullying other PCS, because I already know how to do that, and I like to make the assumption that most people on this forum do as well. We're all capable of running RPGS where foxes and hens join forces, or the ghosts of Churchill and Hitler have to work together to save the earth from alien invasion, or whatever. If I needed help with those issues I would have posted a thread called 'help! my players are out of control and the PCs keep killing each other!'
What I really wanted to talk about was that there is an inherent tension between CSM and humans working together, and I was interested in how people would deal with this in game, such as: how would CSM rationalize/justify treating humans as equals or allowing them equal say? How would mortals earn the respect of CSM? Do people think a certain amount of arrogance, disdain and internal conflict would be a fun element in such a game? How would the GM and the players construct a world in which a mixed CSM/human party functions, etc? Simply saying 'the PCs have to get along because this is an RPG' is not very helpful, especially if it begins to imperil believability.
So to the CSM out there, I guess I'm asking you, in character, why don't you squash this puny mortal's head?
Also, thanks to the many of you who have contributed some awesome ideas and explored many of the reasons why CSM and humans would work together.