Forgive me for a little mini-rant. I've been sitting on this a couple of days and am having trouble shaking it. People who choose NOT to eat meat are not freaks. They are not any more difficult to have as guests in your home than any other person. I don't understand the panic and dramatics of otherwise perfectly pleasant people.
"Oh my god! A vegetarian at my table!! What am I going to do??"
You just serve a meal and there is no need to apologize when they pass on the meat dish. If you are polite, it would be nice not to add bacon to your potato salad. But you don't have to get hysterical and fret about it, and it's not necessary to bring it up again and again for weeks afterward.
Some people choose not to eat meat.