The coach's viewpoint is going to be that they know that Moore can play in a regular-season game, so they are going to go with the known over the unknown. They know he's not close to being the ideal backup, but they think he's smart and can keep us in games behind a strong running game.
I'm not saying it's the right call, but they are just not going to make Rush the No.2 unless they are forced to do it.
I like Rush and thought he was an interesting pickup when we got him, but I figured he'd spend the year on the PS at best. That may still be the case, but probably not if he keeps playing like this.
If you want Moore gone, then you need to hope he plays as poorly the rest of the preseason as he did in this game and not as OK as he did in the first one, so Dallas will trade for a different experienced backup.