I've mentioned earlier on PT that when I was a child, we were taught as girls to curtsy and the boys were taught to bow and we did it before our elders and those in positions of respect, such as teachers (we did it every morning before class started) and clergy. The bow was more of a shoulder tip and not completely from the waist which is subservient. Cultural customs should be taken into consideration but a complete bow from the waist, IMHO, should never be done by a head of state. A shoulder tip should suffice. Whether or not that is the intention, it shows subservience and we do not need to send that message now or ever. To be subservient indicates your inferiority, not as a human being, of course, but in your position whether in social standing or political standing. Even if it was a friendly gesture, "familiarity breeds contempt".