How does David think his grandfather will react to the news of Franks indiscretions? How does he react?

David believes that his grandfather will set his uncle straight.... instead, he defends him.

Yes, tell him, I thought. Tell Grandfather. Tell him, and he’ll take care of everything. He’ll grab Uncle Frank by the shoulders and shake him so hard his bones will clatter like castanets. He’ll shake him up and shout in Frank’s face that he’d better straighten up and fly right or there’ll be hell to pay. And because it’s Grandfather, that will be the end of it. Frank would never touch a woman like that again. Tell him.

Grandfather laughed a deep, breathy cuh-cuh-cuh that sounded like half cough and half laugh. “Come on, Wesley. Come on, boy. You know Frank’s always been partial to red meat. He couldn’t have been any older than Davy when Bud caught him down in the stable with that little Indian girl. Bud said to me, ‘Mr. Hayden, you better have a talk with that boy. He had that little squaw down on her hands and knees. He’s been learnin’ from watching the dogs and the horses and the bulls.’ I wouldn’t be surprised if there wasn’t some young ones out on the reservation who look a lot like your brother.”