I think that a species possessing the technological advances necessary to conquer intergalactic travel would also possess the social awareness needed to see that survival can be attained mutually.
The problem with the world(and by this I mean our world) is that it's too tightly packed in. Too many clashing cultures and races. Diversity is certainly an admirable thing to strive for, but it has to be contained. If you compare the crime rates in countries like Japan to the crime rate in the United States(or other countries of similar diversity), the difference is astounding. Civilizations need to be more condensed and spread out; something that can be easily achieved when you have an entire galaxy that's acessible(due to aforementioned space-travel advances), rather than just one planet.
