I would for the pettiness and poor choice of action
Not for the reason
But yeah, pretty stupid to enact complete oblivion just to spite one princess ...
Seeing as obviously targeting her alone would have been perhaps a more effective route... As she could apparently out perform or out last her adversary - Equestria didn't have to burn for it ... Even if the ponies all deserved it in some way ...
Besides, what kind of message would have been sent if the "princess of friendship" is outright defeated and even disabled - destroy her power- indefinitely in single combat by an unidentified assailant?
It would shatter the delusion glimmer allegedly wanted to destroy in the first place
So much potential... So misguided .... Even when it's being selfish
Hell, glimmer could have planted ideas throughout history that would have birthed a movement of ponies into rejecting the status quo for its convenient oversights and effectively even prove princesses to be painfully vain redundancies
So yeah, forget about being childish and let's just settle for sanely reasonable