He's not sure there still wasn't an insult to Lucifer in whatever Kyle warned Istredd about, but that'd just be par for the course. The only person Lucifer's had to 'defend himself' to was Jack Townsend and even that, strangely, was a sensible conversation. Well. Sensible where the two of them were involved, that is.

"Stop," he says simply. "And think."

This from someone who had been bound up in story and prophecy and had his long-game stretched out under his own power and yet a controlled descent by someone other than himself. This from someone who despite going full reckless-abandon knew where the marbles would scatter when he kicked through a pile of them. That could see the sprawl of the consequences of his actions, he just didn't care about them.

It's as he thought the day he forced Istredd's hand to form the bond:

So many people that were so smart, but so very dumb.

It shouldn't be so easy as 'stop and think' but then does Istredd, ever, really stop? That right there is the hard part. To just stop moving, stop being in so many different places at once, and really think through the cost of what he's doing for the things he wants.