User blog comment:B214/Question and Answers 6/@comment-3965848-20161128172019/@comment-9595671-20161129043407

I get what your saying there, even after healing from Raynare, her actions towards him had a strong effect on his views of right and wrong. The whole date and her being his girlfriend was essentially just using him.

Rizevim's beliefs being incorrect are because of the underlying reason and purpose behind his actions. He wants to be remembered, but in a way that brings suffering to many, then there's his view Devils must be evil, ignoring the fact that all Devils have a choice, like how Azazel chose to fall.

Also, I think when Issei felt Diehauser was wrong, it was before he was aware Diehauser would double-cross Rizevim. True he did reveal the corruption, but at that moment all of Qlipphoth was trying to free Trihexa and since he was helping Rizevim...

Well that makes revealing the corruption seem kinda questionable, if only because it wouldn't make much sense to expose such a truth when your 'helping' to unseal a monster that can end the world. That's not related to justice as much as logic and possibly one's sanity.