Defied: The Wave Motion Gun is destroyed before it can fire.
Discussed: "Oh no! Dr. Evulz destroyed the Earth! But wait, if the Earth is gone, where is he gonna live?"
Conversed: "Wait, what did he gain from destroying that planet?" "The writers thought more people would see it if the movie had a big explosion"
Deconstructed: The debris from the planetary explosion end up destroying Emperor Evulz ships in the vicinity and damaging near by planets in his empire. Further more the empire is denied the valuable resources it would gain from capturing the planet instead. The power needed to blow up the planet makes the Wave Motion Gun horribly inefficient, and it turns out killing off the planets population through other less costly means (such as a Colony Drop) would have been much better.
Reconstructed: However it turns out that Earth Shattering Kabooms are great for rubble mining, and it's the only way to destroy the hostile alien races homeworld that's protected by a massive Beehive Barrier. As for Evulz men, well he has reserves.