Depend on when you bought the TV.
If it was after the HD ready definition you quote was accepted by the store then you would have strong grounds for arguing that the TV was not as described (HD ready).
However if you bought it before the definition was accepted it might be more difficult, unless you could show that 'HD ready' was generally used, at that time, to mean what the current definition states.
I am no expert on HD TV, but I recall discussions, some time ago, about confusion over what HD ready meant and this was why the black HD ready logo was introduced. click here