One of the common consensus among expats in Beijing is that the Chinese are a very rude people, yelling and spitting all over town.
I offer this portrait from a morning commute: a woman standing on a bus opens the window. The man sitting by the window leans over as she sticks her head out to cough out a wad. She pops back in, closes the window, and the man returns to his sitting posture without the slightest trace of resentment on his face.
That, my friends, is courteous behavior.