Come to think of it, I haven't tried playing for guilt.
"Really, I don't mind so much: if we start late, I get paid more. Works out beautifully. But what happens when we go up late is that the actors, who have been at places for ten, fifteen, twenty minutes, they start to get anxious, they start to get bored, they start to worry and they eventually wander off and turn up in the green room, in their dressing rooms, out back smoking... you know, as actors do. It's a big enough hassle to get everyone to places to start with, and having to keep them there for an indefinite period of time is even more difficult."
It's a slight exaggeration, but pointing out that it's creating problems for other people might be sensible, and if I'm careful with my phrasing, it won't seem like I'm disciplining him, either. (Which I can't do, nor do I really want to do.)