Validity of ionic resonance structures
I can't imagine anyone arguing that ionic resonance structures are invalid.  The often contribute significantly to the structure of a molecule and help explain the various physical aspects of the molecule.  The following ionic resonance structure contributes significantly to the description of the carbonyl compound.  $\ce{NaCl}$ is not totally ionic and is described by a blend of both the ionic (major) and covalent (minor) resonance structures shown below.



Resonance structures with a positive hydrogen (proton) are important in explaining hyperconjugative effects.