"You were drinking!" Harry said, not quite arguing. "You don't drink, D. Not when you've got things to be doing. You drink when you've got things riding you. It doesn't take a private eye to work out that one of those things was Murph. I wanted to make sure you got home safe, and maybe spend a little just able to talk to you on the drive."
Then his gaze hardened. "Damn right, I'm going to go back to her. To ask her what the hell crawled up her ass. She's got no right to treat you like that. It's my home, so it's my job to protect you from that kind of hostility. And don't start on how you don't need my protection. You're a guest in my home, and so is Murphy. It's my duty as a host."
He might have lived more in the modern age than other wizards and most of the supernaturals, but Harry was still a firm believer in the Old World rules of hospitality.