That's kind of the killer response to the people who advocate for progressive interpretations of islam.
Actually, at the time I didn't find that to be such an impressive response, and I usually just had to point to a bunch of unrelated examples where "the majority" had believed x in the past and it turned out to be y, or that if sheer numbers of people believing something made it true, we ought to pack up and jump over to Christianity, so on and so forth. Also, there's some hadith I'd like to use here and there, and a verse in the Quran cautioning against following the majority on Earth, blah blah blah. It wasn't that tough, just an annoying barrier we had to break down before we kept going on.
But the funny thing is how significant it became in retrospect. I still would reject the idea that the majority dictates the truth of something, but this question kind of became the crux of all my current issues with Islam. I can say whatever I think Islam is, and that's fine. Maajid Nawaz can say whatever he thinks it is, and just from reading the comments on this thread, it sounds precisely like junk I was saying in the day, and that's also fine.
But at the end of the day, the truth is that he and I is/was walking against the current. Doable, but tough, and at a certain point you and anyone with intellectual honesty must admit to themselves to some degree that this isn't the direction you were meant to be going. The obvious interpretation of Islam is, unfortunately, the nastier one.