George, I really cannot imagine anyone (not even your good self) being "horrified" because a vegetarian is coming to dinner, any more than I can imagine anyone being horrified if a Muslim, or a Jew were coming. We live today (thank God) in an inclusive society, and about the only people I can think of who would induce a sense of horror in me would be those who would ask to be served dog, or cat, or some other domestic animal that I mentally associate with affection rather than with food. Would you really be "horrified" if you knew a vegetarian was coming to dinner, or would you do what I think most people would do, and ask yourself "I wonder what I can serve him/her that will be enjoyable, different to what he/she would normally eat, and easy to prepare in view of all the other dishes I have to make" ?
** Phil.