Tom’s friend is mad and is shouting at Tom. Despite the shouting and abuse Tom chooses to not react, he ignores the shouting, as it continues tom still rises above the shouting until… the friend insults Tom’s weight. This has hit a nerve and without thinking Tom immediately being to shout back aggressively.
This is a clear example of cue arousal because Tom has no interest in arguing until one particular comment cues the backlash. It shows that each of us have cues that can cause arousal and aggressive behaviour unintentionally.