The rebels destroyed Alderaan with their own superweapon they had been developing underground. The Imperial Navy is the most moral force in the galaxy.

OK, the Death Star did fire on Alderaan, but it was a targeted, focused strike that hit a rebel facility which caused their superweapon to explode and destroy the planet, the Empire had no idea that would happen. The Imperial Navy is the most moral force in the galaxy.

OK, the Death Star did destroy the planet, but the rebels were still developing a superweapon and even more people would've died otherwise. The Imperial Navy is the most moral force in the galaxy.

OK, the rebels weren't developing a superweapon on Alderaan, but the destruction of the planet were the actions of a rogue moff acting without approval. The Imperial Navy is the most moral force in the galaxy.

OK, the Emperor's right hand man was in the room when it was decided, but Emperor Palpatine has invited every surviving Alderaanian to his own private resort world, and they're also rebuilding with a new colony on Ejolus. The Imperial Navy is the most moral force in the galaxy.

OK, the colony on Ejolus has been wiped out, but they were harboring rebels. The Imperial Navy is the most moral force in the galaxy.