I know you have several irons in your fire about what you want to do "next"; I'd plot out a few and have that discussion with your advisor so if they really want you, they have to work for you! It's a two-way neighborhood and you don't want this idiot in your environs and looks like you will graduate/go on for your doctorate and he won't be ready? You don't have to get into an argument with the advisor about his work, whether he's "worthy" or not but you do get a vote about who you want to work with and they have to make a decision if they want you or him; they can't have both?