It's wrong to hold a grudge over trivial matters.
Sam is a teacher, and he finds out his entire class cheated on a test to a minor extent.
Sam wants to hold his class responsible for breaking the rules.
Sam decides to take 10 points off of everyone's grade and forgives his students.
Sam decides to fail all his students for the entire semester and decides he hates his class forever.
Sam's students accept what they did, learn their less, and are grateful to Sam.
Sam's students think Sam is overreacting and protest the decision to Sam.