Mynameisalie please dont feed the trolls, i like your ideas.
EdIt: Personal insults are violations of Rule #1. -Mannahnin
back to the topic YES the Imperium is xenophobic because all alien races encountered by them are hostile towards them in some way. BUT there are many examples of the imperium working with aliens (usually on the "common enemy" basis). Here are some examples:
Eldar - 12th Black Crusade
Tau - After a Necron Tomb World awoke, tau joined forces with Ultramarines to defeat them. (
SM codex)
Orks - Blood axes are mercenaries. 'nuff said.