Each must play his part.
I think the great thing about art is that it is open to multiple interpretations, and it can be interesting to compare and contrast. Ultimately, it is about inspiring the interpreter, and not about beating down imagination.
And of course great themes can be reinterpreted as we learn and grow, or even with our moods. I think however, that your son should follow His heart, and continue to think about art from his own unique perspective. From what I can tell, he has a good perch to gaze from.