What I was taught when I was young was that his listeners found his sermon offensive because they thought he was talking about cannibalism, but even back then, this seemed like an overly simplistic explanation. For one thing, I had no problem understanding that he was speaking figuratively (or spiritually, for those of you who are transubstantially oriented) and I was only a kid. For another thing, even though the story does suggest that some people took him literally, these were members of the crowd, and people will entertain all kinds of urban myths. It’s another matter entirely to leave the Messiah that you’ve been following based on such a flimsy misunderstanding. (Do you really get no satisfactory explanation from any of your fellow disciples?) So, my main task in this play was to portray this mass exodus in a plausible way.
In order to do this, I emphasized aspects of the story that I do think are really there, but which modern Christians do not perhaps notice much. The sermon is repetitive and rambling, and has a megalomaniacal quality about it. Afterwards, when his disciples express difficulties with it, he attacks them rather than explain it to them, uttering hard words about how some of them are chosen and some (presumably the ones who left) are not. All this is there in the text, and taken together, forms a much more believable explanation for why disciples would leave him than any child’s misunderstanding about cannibalism.
One way in which I go beyond the story as told is having him go back to the synagogue the next day, with a chance to make his words more clear, but repeating the exact same sermon! This does not happen in the original story, but I thought it was very much in the spirit of the original sermon.