yelling
Explanation
The Joke
In the first panel, a child runs to her mother crying, "Mom! Bobby's pulling my hair!" The mother calmly explains that Bobby is a baby -- he can't think like the older child, he doesn't understand, and therefore screaming at him will do nothing. It's a perfectly reasonable, patient piece of parenting advice.
The comic then cuts to "Later..." where the same mother is at her computer, furiously screaming, "NO! I hadn't saved yet. FUCK YOU, Microsoft Excel! By Christ, FUCK YOU!" -- yelling at software that, much like baby Bobby, cannot think, doesn't understand, and will not respond to being screamed at.
The Humor
The comedy comes from the blatant hypocrisy of the mother's behavior. She delivers a calm, rational explanation to her child about why yelling at something that can't understand you is pointless, then immediately violates her own advice by screaming profanities at a computer program. The joke taps into the universally relatable experience of losing unsaved work in a program like Excel and the irrational rage that follows -- everyone knows the software can't hear them, yet they yell anyway. It highlights how adults are often no better than children at following their own advice when emotions are running high, and that our logical understanding of a situation completely evaporates when we lose a spreadsheet.