Istredd is used to pretty much any reaction to his situation with Lucifer. Everyone from his world is skeptical or horrified by it, and then there are the people from Earths who have devils of their own. Istredd doesn't have one of those but he probably wouldn't care if he did. He's very good at being logical about these things.

"He's probably trying to be annoying to Castiel, who doesn't love that we're together." The angels are all very childish when it comes to one another and Istredd's gotten used to it. "Castiel and I were captured together, we bonded closely, he trusts my judgment even if it's the opposite of his own." And that is why Castiel told Gabriel how much he trusted and respected Istredd. They had trauma bonding of the highest order. They lived through something terrible, side by side.

He curiously observes Gabriel though. "You're an interesting one though. I know his opinions of the others extremely well, he complains about them, but not you." Istredd finds that fascinating. It isn't that Lucifer is without the same anger about a brother who didn't follow him, but it's different with Gabriel. "You don't seem as angry at him either. Could it be I've finally found a brother who doesn't hate him?"