...and that's exactly the point.
I don't have a problem bowing to a picture of O Sensei, but then, I was raised in a tradition that holds the concept of graven images rather lightly, not granting them undue significance either way. What offends you more: someone who bows because bowing to a picture of O Sensei is meaningless to them, or someone who doesn't want to bow because bowing to a picture of O Sensei is idolatry to them?
I'm not ofended, I'm open to everything, I think most of the newbies bows but don't know who is this old man on the picture and I do understand that there are guys who doen't bow for the reason you wrote, not in our dojo and I never met one, but I know they exist and perhaps would not understand the meaning O'Sensei has for Us? better for me and the people I'm training with, we are like a family, the question is, I will ask if my sensei would accept anybody who doens't want to bow..
I' could'nt train today, cause my car stroke on the highway