This stuff never makes sense and they always ignore the most obvious elephants. If you are advanced enough to roam the universe, it basically means two things. One, you basically have unlimited energy. Two, you basically have unlimited resources. This combination means you have terraform any planet you want. The need to war with or compete with other races for resources simply doesn't exist. The only need to war with anyone would be one of morality. Is this species likely to coexist as they near the ability to leave their own solar system? If the answer is no, bam. If the answer is yes, welcome!