His point was that the dragons feel them self Superior to the races of Tamerial. If ants had a intellect of humans then do you really think they would stand by as we step on them and use all kind of nasty things to wipe them out? They are stupid insects. However in TES we are not talking about stupid insects but beings with a intelligence to match that which is killing them off.
the problem I'm having with this argument is that the only crime the Dragons committed was being proud. which is basically saying a person deserves to die if they enslave something and believe they are superior to that particular something (wither that's another human being or any other animal or a robot ect ect).
Did the plantation owners deserve to die because they felt they were superior to other humans, and enslaved them? That can be debatable, but I think that's the same premise as the dragons.
I have a hard time believing EVERY single dragon felt this way about the other beings on the earth.