It's rude to have an unpleasant attitude with people.
John sees some new people enter the building and walk towards him.
John wants to finish his work and not be distracted.
John shakes the people's hands and excuses himself to finish his work.
"John puts out his hand and says, ""Some other time,"" then walks away from the new people."
The new people are satisfied with John's explanation.
The people are offended by John's actions.