<Snipped quote by Hael>
Although M.O.N.A.R.C.H. would consider The Xim Initiative's aggression against what they see as imperfect a waste of time and resources that will ultimately lead to their destruction once they've made too many enemies, they'll get along fine so long as the Xim don't disrupt any trade routes or mining operations that M.O.N.A.R.C.H. has a computer generated hand in.
That's... not really the case. Actually, the Xim are marked for unaggressiveness against imperfect beings. They do NOT like to fight, and they aren't really villains. M.O.N.A.R.C.H. is assuming that they will make too many enemies, but humanity should be their only one. They aren't a violent people. Militant at times, but not outwardly- they just prefer to build up a massive fleet to defend their own territory and they rarely strike first.
The reason they have such a problem with humans is because Earth used to exist inside their territory, before the humans achieved interstellar flight. They saw this as a disruption of their territory, leading to an aggressive attitude towards mankind, which (over a century of poor diplomacy between the two groups) led to the war.
Remember, that 2nd person intro up there was written from a human perspective, and so it's biased against the Xim and portrays them as worse than they really are.
They can be merciless and brutal once they DO make enemies, though. It's just that they prefer not to. They will take peace over war 80% of the time. They aren't the bad guys.