ah, yes, a rational adult

I ask my son if he wants to come over for Christmas; On the day he texts me and says he will be coming over, I just reply with generic niceness and neglect to tell him that I am currently in my car on the way to the doctor; When he asks me why I didn't tell him I was in the car on the way to the doctor, I get all defensive about it and act like he's the inconsiderate one here; Why is my son so disrespectful