hmmm....wouldn't that be a twist? The race that supposedly we look to to save us, and rescue us, turns out to be an overly manipulative, controlling, panicky freaked out quasi-communist regime. And here we thought the Yeerks were bad. Only to discover that since we didn't know all the information...we defeated one evil race for another.
Here are my thoughts though about the dangerous government. Evolution wise, those blades are deadly. Even if used for mating, we know they're sharp. Even earth animals can use their horns for defense. So what I think is this, and this is the most logical to me, they evolved to fend off huge predators.....until they evolved enough intelligently to start making weapons and other things.
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..then through overpopulation of their cities (didn't they have cities at one point and then they cut back? this might also explain the children policy the government seems to control), pollution, lack of care of their planet, overtaxing resources, and what have you they wiped out those animals simply the way we are wiping out our own today.
This may also explain why the Andalites seem to have re-entered this hippy, nature-worshipping, planet loving phase. Their learning from past mistakes.