I'm really wondering what that goddess is aiming for in pushing Allen in this direction. In most fantasy stories, demons and demon lords are depicted as beings that oppose gods and deities (heck, it shows in this story the name of the '7 demon lords' that are titled after the deadly sins that God would normally never forgive). To have this goddess do anything with demons, even indirectly through Allen, maybe she's not your typical 'good' goddess that only wants what's best for humans.
I might be overthinking this with the series being mainly a comedy, but it's something you can't help but wonder.