Try this on them.
A common question an interviewer will ask them is 'What is your greatest weakness?'
This is because 100% of pre-med students are ... pre-med-student-like. Their answer is, inevitably, 'I'm a perfectionist. Everything about me just has to be perfect, or I work like insane to make it that way.'
Don't you find that incredibly aggravating? Isn't that the same as saying 'I'm perfect, I have no faults?'
Here's your new reply: 'So, you're saying you constantly strive toward an impossible goal and are faced with the continuing failure of your existence? How's that working out for you?'