Question

Pure water is neutral. What is the appropriate justification for this?

Answer 1

When you say neutral, are you then referring to electric charge, pH or something third?

Answer 2

H20 ---> H+OH−

Pure water dissociates as above(slightly) to give equal concentrations of H+(acidic) and OH-(Basic). So they neutralize each other and pure water is thus neutral.

Answer 3

You forgot to mention that we've set an arbitrary scale, pH.
When [OH-]=[H3O+]=7x10^-7, at 25 degrees, pH=-log(7x10^-7)=7,
which we've appointed as neutral.