Someday I'm just going to get smacked by a stranger

Exchange between a couple at the blood-pressure cuff in Target:

Him: Just put your arm in it.
Her: Okay. Don't squeeze it!
Him, patronzing: I'm not going to squeeze it, but it's going to squeeze. That's how it works, it's got to press to get a reading.
Her: Don't press that twice!
Him: Calm down.
Her: I don't-
Him: And no talking!
Her: Don't tell me not to talk!
Me, safely out of earshot: Thaaaat reading's going to come out higher than it should.