I was taught to laugh in the face of my tormentors, but you are right in saying that it is better to look them in the eye and calmly explain that it is not funny.
ولكنكم مُصيبون بالقول انه من الافضل النظر في عيونهم والشرح لهم بهدوء ان الامر ليس مسلّيا .‏