"Maybe there's hope. Father isn't the king here, and if this other prince could marry whoever he wished.." Arthur would probably still seek his father's approval, though, and Uther was stubborn in his beliefs. Still, Arthur would choose to be hopeful. It wasn't exactly an issue now, since Gwen wasn't here.
"Right.. Well. We should go about getting you set up to be my servant here!" he said, slapping Merlin on the back. He was completely ignoring Merlin's earlier hesitation.