Crowley had to wonder what Michael meant when he said that he would 'correct' Castiel. He himself might have been a demon, but he was no stranger to how they 'rewired' angels, after all he'd hacked into Samandriel and Gadreel's operating systems himself, and he knew when he was tinkering around in little Alfie's head that that was Naomi's handiwork. Somehow, Crowley doubted that Michael's justice would go quite that far. After all, he was an officer of the law and while he couldn't very well go and kill Castiel, he would most likely do something that would leave lasting damage.
In hindsight, Crowley would ask himself if he told Michael the truth with no hesitation because of his jealousy towards Castiel and Dean's relationship. While he was a demon and he was no stranger to jealousy, that was something that had actually never crossed his mind. There was a bitterness towards Castiel, but it had nothing to do with Dean and more to do with the fact that he never truly paid for the way he'd betrayed Crowley more times than he could count. Crowley knew Michael couldn't kill him, so what was honestly the worst that could happen? Dean would be pissed at him? The motley crew of hunters would attack him? Whatever.
He'd nodded mutely when Michael told him he needed more than his word, understanding fully. He could have given him a short burst of magic, a memory spell in order to show him everything that went down, but that was more invasive than a tap on the arm and he didn't want to test him more than he already had.
"Believe me, I have no desire to get involved in any of this at all," Crowley shook his head, "It's your business, and Raphael was your brother. The four of you, brotherhood... family, doesn't come close to describing it, even with everything," Crowley shook his head. It wasn't his business, but he was making his point. "I get that you have to do what you have to do but just... be careful, alright? The Winchesters, they're happy here, they've got this perfect little slice of life, it's saccharine and mundane, but if you think they were dangerous before, they'd be more so now that they have everything they want. And they have friends in high places." He cast a furtive glance outside as if expecting to see Jo Harvelle looking at him through the window. "I get that you need to do what you have to do. But just be careful about it."
Crowley felt a little awkward saying it, but he found he had a grudging respect for Michael, something that had evolved from a sense of pity and disappointment that he was stuck in the cage and shunned by Chuck, used up by Lucifer and the Winchesters and at the same time with a decent enough head on his shoulders and a moral compass that could help Crowley steer himself in the right direction. Only in a place like Preya could he find himself starting to make friends with the someone like this. And perhaps, spitefully, he thought maybe the Winchesters couldn't be the only ones who could have friends in high places.