Even if the polygraph examiner is not abusive, the whole process is stressful, especially to "Type A" people. It's designed to be stressful. You are under constant surveillance, and they make sure that you know this. They make you wait for a long time before beginning. They keep the rooms cold, so you aren't comfortable. They don't let you wear a jacket, because "it could interfere with the equipment." The chair is uncomfortable, and the sensors (especially the blood pressure cuff) are deliberately too tight. My arm would often turn purple.

You are obligated to keep coming back until they say you're finished. More often than not, they will not tell you that you "passed" the exam.

I always had issues with their "baseline" question where they tell you to give an incorrect answer. They've told you to lie, and they know that you're lying. I have no stress at all in that situation because everybody has agreed and knows that I'm expected to lie. For some dumb reason, they are looking for some sort of physiological response from me that indicates deception. Maybe some people will react subconsciously, but I don't.