That is a bit like saying that because Britain and France declared war on Hitler in 1939 that it makes them the aggressor.
No, Kabrinskia broke the treaty, that makes them the aggressor.
What Treaty? All I remember was a declaration of closed borders that was never put to paper (no treaty was sent to us via game mechanics that I know of) A treaty takes 2 or more parties that agree on something. All Terran did was say stay out and then invited a trader to trade and used that and a priests travels to declare war.
NO, Terran is the aggressor in this war.