It's mean to purposely hurt people's self esteem.
Mindy is asking John, her husband, to show her how to use the new laptop.
John wants to feel good about himself and smart.
John writes some instructions down on paper and gives it to Mindy, saying she'll pick it up in no time.
John says to Mindy he can't understand how she doesn't know how to use it, and she must be dumb.
Mindy feels John loves her and feels happy and confident in using the laptop.
Mindy resents John and feels sad and isn't confident using the laptop.