Geezus, what a stupid ass hole.
Your son in law, Patrick, not you.
One of the most basic values we learn as young people, that we carry throughout our lives, is to honor our commitments. His team is counting on him. If his own father is teaching him that that does not matter, well then, the poor kid has little hope in this regard.
I would almost suggest it might be something you can help the kid with, as someone he knows and respects. Granted, I am not yet a grandparent, but I think I can appreciate the dilemma this presents to you. It's got to be very uncomfortable telling a grandkid that his own father is wrong about something, and I'm sure you want to maintain a good relationship with your daughter, at least. Tough situation, Patrick. You are kinda between a rock and a hard place. Good luck... to both you and the kid, especially.