I mean: God let the mistake be done by the Prophet without the angel telling him: this is wrong.
Like what Jonah did and David did for example.
I mean: God allowed this to occur, not that He made it lawful to the Prophet, but He let it happen without alerting the prophet to its wrong: to make this a lesson to people that the prophet is a human like them, and he might make mistakes.
That's still countering the idea that God is a Good God if allowing the prophets to make mistakes that could be linked back to God.
The excuse "God allowed this to occur" is an excuse that anyone could use for anything.
When someone is a prophet they're supposed to be "better" than regular people because they have that connection to God.
If they're not, then they're just like anyone else.