According to Semi-Gaia Life Adelie, the Adelie Civilization had suffered a completely unprovoked disaster. They had trusted the first Level 5 Civilization they encountered, only to be used as experimental subjects by that civilization while dreaming of peaceful coexistence, until their entire civilization was reduced to ashes.
The Adelie Civilization had simply been unlucky. They had developed all the way to Level 4 Civilization without encountering a single Alien Civilization, and the first one they met had been an advanced civilization—an Evil Civilization at that. Though perhaps it could not be called evil. From that Level 5 Civilization's perspective, what they did served their civilization's interests. To them, using the entire Adelie Civilization as an experiment might have meant nothing.
It was like how humanity, after defeating the Kun-Tai Civilization, had exterminated all the Kuntai People from the Kun-Tai fleet while leaving only their newborns behind. Humanity did not consider itself evil. Of course, humanity had been paranoid back then, always fearing persecution, and it had been the safest approach. If they had not done so, humanity might already have ended up in some Small Universe within the Silver Heart Alliance.
There were no what-ifs.
Nor would humanity now judge other civilizations' actions solely by its own morality. What good and evil existed in this universe? They were merely conclusions humanity reached by measuring other civilizations against its own moral standards.
Perhaps, to that Level 5 Civilization, what they had done had been the most correct and righteous course of action. Perhaps their civilization's culture was simply like that. Their individual lifeforms might even have been creatures that devoured their own kind, so once they ventured into the stars, they naturally considered the destruction of other civilizations perfectly justified.
Humanity had already encountered many civilizations. It was no longer the