User blog comment:FairyRaven/Fairy Tail Chapter 336: In Order to Live Today to the Fullest, Review and Commentary/@comment-65.5.162.141-20130622064704/@comment-1359322-20130622065701

Actually comparing Obito and F. Rogue isn't that wrong but isn't right either, Obito was a positive thinker until Rin died, F. Rogue tried to be a caring friend after Sabertooth lost but failed with Frosch's death.

Well there's also what Future Rogue said, there are no longer guild available to fight Acnologia not that they're useful anyway but maybe being the last living mage made him go all crazy.