I don't really buy this. Being on time is common decency. Asking someone to be on time (especially someone who *is* capable of it) isn't asking for some profound change in regards to who they are on some fundamental level.Does he really have to change for you?
And for the record, most of the time, I just bite my tongue when he's late and let it slide. He was just *so* late today that I couldn't bite my tongue.