This joke works because plot means to draw a graph to visualize information, but it also means to scheme, to plan evil, to hatch a sinister plot. The joke works because a math teacher can plot a graph, which could be involved in plotting a crime, but not usually, which makes the speaker seem suspicious, and in a silly way, as if the plan of the graph could be the plan of a crime simply because the word plot is used to say both. It is possible our math teacher is planning a bank heist, with the suspicious graph. The math teacher is certainly plotting something, the graph, and what is normal isn’t suspicious. This shows us the word plot is used by us in two ways, and the difference is fear, suspicion that a plan is more than a plan, it is a plan for evil, and we brace for evil with fear. A plan is someone being calm and resolute in a way, and a sinister plot is a plan, a resolution, that others fear. The turn from a calm, normal, plotted mathematical situation to unreasonable paranoia and aggression is the jerk of the joke. If we look at language use in particular situations from a pragmatic perspective, and keep an eye on the situation of emotions, and how emotions can change, we can understand what jerks us around and makes us laugh at some jokes and not others.
Many people believe that there are exclusive and separate human races and that some races are naturally smart and kind while others are unintelligent and mean. This is all mistaken, modern day mythology. There is more genetic variation between individuals than between ethnic groups. There is no genetic evidence that some ethnic groups are smarter or kinder, and individuals can increase their intelligence and compassion throughout their lives regardless of their genes.
The interactions we have with others create categories and frames in our heads that mislead us into thinking that certain types of people are smart or unkind and mislead us into treating them as separate types of people. Neuroscientists have shown that within milliseconds we identify others by ethnicity, gender and age, before we have a chance to think or speak. This can negatively frame our thinking, communication, and interactions. We naturally show frustration and negative emotions when we consider someone a threat, and this reinforces these reactions in ourselves and in others, including children, whether or not we’re aware of it. Psychologists have shown that we are all somewhat racist, the privileged and disadvantaged, some of us more so, and some less so. We are all imprinted with negative attitudes towards ethnicities who share our common culture, even if we actively ignore it in ourselves or live where racism is far more covert than overt, more thought to oneself than spoken out loud.
As Europe rose in wealth and power over the last five hundred years, Europeans dominated Africa and the Americas and labeled Africans, Latinos, and Native Americans as savage and inferior. We’re still dealing with this today. In our diverse society, it is mentally and physically healthier to talk about our problems rather than ignore them and to discourage the idea that we are on opposing teams. When we focus on not making mistakes, this has a negative impact on our thinking and the perceptions of others, but when we focus on having a positive and open interaction, this is good for thinking and communication. Positivity helps us see each other as individuals and not as categories. Understanding that our thinking and personalities are not fixed, but can be enriched and developed, helps us to identify with each other and thrive.
Confucius said that if you put yourself with any two people at random, you can take their strengths as a model to follow and their faults as a warning. This is wise advice, as we all share similar strengths and faults. Intelligence and compassion are human virtues. Ignorance and brutality are human problems. We can see these are valued and useful yet difficult to develop in all human cultures, ancient and modern. Just as genetics shows we are actually one race with a variety of interrelated ethnicities, we share one culture with many cross-pollinating branches of subculture. We can draw on excellent and terrible examples from all of humanity to become better people. While this may seem obvious, it is easily forgotten.