Shrug. I would — and have — had dinner with all kinds of people whose beliefs and behavior diverge sharply from what I think is advisable or ethical. Having dinner with someone is not an endorsement of their worldview, full stop.

Maybe this will sound corny, and I guess it probably won't land with non-Christians, but I'll offer my heuristic anyway: What would Jesus do? I don't think shunning is the answer.