The most disarming thing you can do to someone is try to understand their point of view... i.e. "Cyclists around here been frustrating you lately?" It's really difficult for someone to stay angry when you respond by trying to understand them. I'm far from perfect at this myself, but it can help diffuse tension and may make them a little more tolerant of other cyclists in the future.

Still laughing from the first response... "After 50 miles..."