As awesome as Gaius is, his worldview is essentially Darwinian: Might makes right, and only the strong should rule (and by strong, I mean through force and conquest) He acknowledges that you have the strength to be a ruler if you wanted, but people with this mindset rarely bow to greater strength, they just seek greater power. Even if you had rescued him, he would have redoubled his efforts to conquer Eorzea to prove his right to rule.