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  | some people talk about the expressive superiority
  | of tonal music based on its "natural" basis.

People with a spleen for simplistic views of the world, yes. 

  | Though difficult to prove, maybe we think something 
  | is natural just because we´ve been always used to it.

Not much need to prove that, it's called "second nature".
One of its more common modern manifestations is that 
windows users think windows is the shit.  Aka ignorance.

  | We as composers do require a socially "accepted" basis
  | to make our music understandable (even by ourselves), 
  | this basis is always extended thancks to composers who 
  | deny the preexisting rules ...

I guess if you'd poll enough people and average their idea
of music, you'd end up with the kind of stuff they have in
porn flics: mainly noodle, noodle, noddle, with a little
pepping-up towards the end, maybe.  Beethoven, on the other
hand, always insisted that rules in art may always be
violated to satisfy higher rules, which appeals to me more
than the prospect of Taco Bell music.