I wish WordPress theme authors would get this tattooed to the back of their retina, so they’d be constantly reminded.
Responsive web design solves an important problem: it makes the same content comfortably digestible between different devices. For folks to receive different content just because they have different devices would be unacceptable.
Similarly, it’s unacceptable for a design to dictate the nature of the content. We wouldn’t tell an editor, “Lose that, will you? It makes the design look wrong.”