Re: Urban outs the villain. Maybe.
I think the reason we can't rule out Mitchell, or Khan, or Garth, or Q is because we don't know who's in the film yet. Once we know who's in the film, then we'll be able to rule people out.
“A life is like a garden. Perfect moments can be had, but not preserved, except in memory. LLAP” — Leonard Nimoy (1931-2015)