Upon looking on the wiki...
Nothing on the wiki for Black Zetsu making such a claim, which would be something pretty important to add. I'll check Kaguya.
Looking like a bad translation, nothing on the Kaguya thing.
In contrast to the need to use the White Zetsu as an army for battle, the Wiki states she wanted them for peace:
As time passed, however, Kaguya began to lose trust in humanity as the power ultimately corrupted her. This led to her into madness as she created her ideal peace by trapping her victims in the Infinite Tsukuyomi and convert them into White Zetsu, which would change her public image of a benevolent goddess into that of a Demon (鬼, Oni).
I guess this means Kaguya's plan was inherently good since White Zetsu look pretty darn happy.
Oh and Madara could not explain the origins of the Byakugan and Kimimaro's clan...Nothing a middle-ground latecomer can do to replace the real baddie:
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