I wonder if that is standard Imperial policy, or if that is just an Imperial Guard thing. Since this is conquored planet rather than something like Earth which is actively at war with Gamilas. This planet was probably either rebelling or protesting the Gamilas rule, but instead of subjegation, they just went straight to kill the lacky leader and genocide. I wonder if they could Gamilform it afterwards for the blue skinned citizens, rather than leave a dead husk of a world.
One wonders if Dessler even approves of this sort of thing. Or if he even is informed about it. He seems fairly aloof. Like he has larger things on his mind than the day in day out Empire building. (or he's fantasying about Starsha).
When you think about historically, the SS did the same thing. Of course the only difference was that Hitler approved it. Where as Deslar is like you say.
Of course the only major difference from other series that use mass planet destruction is the fact that they are using not that many ships and a few planet bombs. In Star Wars, the whole planet was destroyed in one shot, while in Macross they came close to wiping out humanity with over 4 million ships. So it begs the question, Who has killed more people now? And Hitler does not count nor any real despots past or present.