Lets say a meteoroid was on a collision course for Earth.
Its over. No space colony on the moon is going to change that. We're toast.
Dont believe the movie bull that says things like "We now have the technology to prevent...bla bla bla", because we dont. Not even close. And exploring space has no applicable science to help us in that situation, unless you consider a small colony on the moon as "help".
Starting a colony of any sort in space serves many purposes, but the most interesting is human life in space. You'd be surprised how biologically dependant Earth creatures are on things like gravity for a natural birth cycle, or a child learning to walk, etc.
The point is, we as a species are nowhere near that point. To pretend that we are, or to prematurely attempt such a bold project is foolhardy.
IMO, life in space cannot exist until humanity has an undersea colony here on Earth. Things need to be proven out. Think about the stupid ...soil. Are you going to fly soil from Earth to the moon? How long does that last if crop rotation isnt adhered to or miscalculated?
No, colonization is not the next step and it wont be in our lifetime. Maybe not even our great-grandchildren's time. Maybe later than that.
We go to space to explore, to learn, to test, to predict, to prove, to enlighten...for perspective. There is no better reason, come what may from that.