What does that have to do with the point being raised? Putting aside the simple fact that we're not talking mutually exclusive elements...it's specifically being outlined that the Garleans have consistently been under attack both before and after forging themselves into an Empire.
Though as Kage pointed out:
It was the expansion beyond reclaiming lost territories that many defectors had an issue with.
That aside, these things are pretty nuanced and we're discussing this from the perspective of the Garleans themselves. As I've outlined many times in the past whenever these very same points were raised, I do not believe that anyone is under any obligation to just roll over and die for the sake of somebody else - however, that extends both ways and I think it's important to acknowledge that the protagonists are conveniently shielded from the need to get their hands as bloody as the antagonists because they are lucky enough to be specifically empowered.
It's easy to take the moral high ground when, upon death, you're revived (in cases such as Y'shtola, multiple times at that).
It's also easy to take the moral high ground when you're able to readily manipulate aether.
It's easy to take the moral high ground when you're not seeing your loved ones freeze to death in an inhospitable wasteland.
It's easy to take the moral high ground when you have a self proclaimed hero and living superweapon who conveniently dispatches any threat before measures can be taken.
Let's put it another way - if, for whatever reason, civilised society collapsed within the coming year in our world and we were all forced to fight - as Drusilla put it - 'tooth and nail' for resources in order to survive, we would no longer have the luxury of current laws and morals to protect us.
Again, it's easy to claim that you wouldn't do X, Y or Z. Yet when you're forced to do whatever is necessary to protect your loved ones and prevent them from being subject to genocide then if permitted to escalate then the situation is going to escalate.