I'm guessing they had a much smaller population than earth did too. Predatory animals need a lot of territory, and theres usually relatively few of them around. Once they really got into war, the birthrate probably went way up, but the overall population stayed about the same. once they all started working together as a race (for the most part) that death due to war rate would be way down, which would explain why they have a definite need to expand to other systems. So they're not all bad, they just need more space.