The first is to point out that, while the Empire itself is pretty atrocious, there are individuals within it who are not. Therefore, calling for the murder of all Garleans is unjustified. Most people don't ask for that, but are often straw manned into it because that's easier to argue against and someone inevitably comes along who does ask for it. Other than that, it's an attempt to paint the protagonists in a negative light for not trying their hand at diplomacy with the Empire despite the fact every Imperial we have encountered thus far prefers aggressive negotiations to diplomacy (even the one who formed an alliance of necessity with us).
The other is using tu quoque ("you too;" appeal to hypocrisy) fallacies to avoid answering the question of whether or not Garlemald's actions are justified. "Limsa breaks their land treaties, just like Garlemald invades other countries. They're no better!" The problem is that what Limsa did there is minuscule in comparison and widely acknowledged as wrong, and this doesn't answer whether or not it's right for Garlemald to invade and subjugate other nations (or at least to the extent they have and continue to). The "Eorzeans don't try to engage the Empire in diplomatic relationships either!" falls pretty well into this too. (We're supposed to try talking to them, even though only one Garlean has tried to talk to us and this was after he tried to personally kill us three times. The others just try to kill us.)