Because each of us has a different perception on what a painting is supposed to express. And since people had a lot of questions and were twisting some things, he felt compelled to nip in the bud and explain fully about the painting, why he did it and such. People were misconstruing what the painting was about. Go to a painting gallery and see the many types of paintings from abstract to realism. You have the artist's perception and meaning versus what the public sees.