This situation makes me more uncomfortable than anything else when I’m dining out. While I try to be a pleasant and courteous guest, and always tip well, I can’t control the others who are dining with me. When this occurs, it’s usually a business colleague or a friend of a friend who I’m dining with for the first time — and hopefully the last.
But that doesn’t make the circumstances any easier. In this situation, I try my best to be kind to the server and if I feel like I can, say something to the member of my party about their rude behavior. I often find it comes from a feeling of entitlement on behalf of the diner. A belief that the server works for you and therefore must earn the tip, often causes the guest to act like a real ass.
If I am the one paying the bill at the end of the night, I try to tip a bit more to make up for the rude behavior. However, if you’re not the one responsible for settling the bill, you’re left in a bit of a tricky position.
You could try and leave a separate tip for the staff in order to apologize for the rude behavior. But that could create its own controversy between you and the offending party. If nothing else, you can simply try apologizing for the behavior as you leave, and make a note to never dine with this person again.