At this point, the ethics of the episode are so topsy-turvy (because they could never support themselves but must pretend to cohesion given the story's actual aim, which is essentially to call bullshit on both Israel and women's suffrage as a matter of children's entertainment) that he's right: That's the only sensible thing they can do, even though it's going to start the war just like she wanted. Oh, Rory. Such a blank slate until the last second, when suddenly you're Aslan. Character development's never been so easy! (Why, I can't imagine why you're being such a huge fucking saint, all of a sudden, throughout this entire episode. Can't imagine.)
Then it gets insufferable and interminable in all-new amounts, as the Doctor sits down Nasreen and Amy with Eldane in order to negotiate the West Ba... I mean, the settlement of Earth. He manages to combine the idiotic We Could Be Heroes thing with the Best Of Humanity thing and the Who Has More Fun Than Us Time-Travelers thing, then winds the whole thing up -- this is impressive -- by applying the Some Events Are Fixed But This One Is Coincidentally A Pivot Point Where If You're Just Magnificent Enough Everybody Could Be Living Where The Streets Are Paved With Cheese For The Rest Of Eternity.
It's like a monkey read five RTD scripts and then got ahold of a typewriter. Why not just tell Amy she's The Most Specialest Person In All Of Existence, for good measure? I think that would be all of them, and it's not like it has to make any kind of sense at all. Just chuck it in, throw some twee music on top, nobody will care that it's so "heartwarming" -- without the "heart" or the "warming" -- that you're basically once again being called a jerk by the show.
The upstairs crew get ready to head downstairs, but first Ambrose just has to do one thing, be right back. Is it a horrible thing? Yes. (Is it also a wise thing? Yes, given that they have no reason to trust the menfolk who've ousted those stupid women that were in charge before.) She gets Mack to do it, after begging several times and finally resorting to emotional blackmail: "If you won't do it for me, do it for Elliot. I know I did wrong. But I can't lose him, Dad!" Moms: Always protecting their kids and fucking everything up and getting vampires raped, when they're not committing suicide over their dead boyfriends.