Is your experience in Midland, TX, in the Bible-Belt? If so, it is quite possible that the person who had trouble "bowing to a picture" honestly felt that it was idolatry, a serious sin. (For some, this sounds like a joke, but for many Christian fundamentalist folk, it is very serious.) One Scriptural basis for this opinion is: "You shall not make for yourself a carved image, or any likeness of anything that is in heaven above, or that is in the earth beneath, or that is in the water under the earth; you shall not bow down to them nor serve them." (Exodus 20).
It probably would not be appropriately sensitive to treat this too harshly. Throughout the world the pendulum has swung all over the place from actually using figurative art for idolatry on the one hand to rampant iconoclasm on the other. Remember the story of "The Golden Calf" from Exodus?
From about 700-900 A.D. there were great schisms and presecutions in Christendom related to "iconoclasm." Even today, the Eastern (Roman Empire) Christians shun sculpture and statues (3-D art) in favor of icons (2-D art). 3-D is just too close to idolatry for some! During some periods of the 8th century, even 2-D icons were considered idolatry in the Eastern Church. This debate was a factor of the mutual excommunication between Roman and Eastern churches that took place in 1054 and remains today, 950 years later.
Also some Islamic communities frowns on figurative art as deceptive and/or idolatrous. This gave impetus to their great traditions of geometric decorative arts. (Recall that recently the Taliban were destroying Buddhist art...) Even Plato felt that figurative are was a deception and a distraction from reality!
I know fundamentalist Christian folks in Texas that feel that even images of Jesus are dangerous, idolatrous objects. So I can understand why they might have trouble with a tradition of bowing to a picture of O-Sensei. You can find many simple evangelical churches with absolutely no art present in their churches.
I have also spent a lot of time involed with Chinese Christian communities, and the whole area of interaction between Chinese cultural traditions of ancestral revernce (not worship, please!) and certain Christian disciplines is very difficult and significant.
I don't intend to say one way is right or wrong, but there can be very significant religious issues related to this topic. How do you teach aikido and take care of the religious feelings of the community you are in? Do we just write them off? Do we adapt our practice to make them welcome? Is the photo of O-Sensei a "non-negotiable?" in Texas?
Peace to you,