Heard in Class:
Stats Tutorial: results from personal class data regression tests show that the variable sex does not play a large role in predicting the weight of people. So the tutorial teacher said that "sex was insignificant". This troubled a lady student who reacted strongly: "how can you say that sex is not significant!".
Come on, it's just numbers...

Stats Class: we looked at the causality between intercourse and pregnancy from some imaginary survey that sprang out of the professor's head (and yes some 5 people in the sample test have responded that they became pregnant with no intercourse)
Microeconomics class: I quote the professor who explained that in game theory, as well as cartel decisions, longer time implications influence greatly short term decisions: "think about other short-term temptations carrying long term consequences".