You know. A simple warning and something such as CRM and CFIT training wouldn't be enough though now, would it?
He apparently failed CRM and CFIT training already, given the gravity of the situation. He's an allegedly fully qualified Captain, not an FO in training.
I've had 2 FOs in the past month use their cell phones while taxiing out. Both of them were new to the airline, though neither was new to the business. I let them know (individually and privately) in no uncertain terms that it would not be tolerated in my airline, and that was the only warning they would get.
I have NO CLUE why it would be tolerated in ANY airline...