I remind you this is the same guy that tried to broil and freeze you with his two little zombie dragons. He's also the guy who removed the blessing of light, allowing the Ascian to enter so he could grab Tsupimati, resulting in an untimely death.
So if not for his meddling, a lot of bad events would never have occurred. Oh, and he wants to raze Ishgard to the ground. I mean sure, they've got history with the dragons and probably deserve at least some comeuppance, but for every guilty there would be hundreds of innocent casualties. Remind me again why Midgardsormr is meant to be a good guy?
...also, wow... it's a sign of good story telling that we're even having this debate. Kudos to the writers.