It's a dead man switch. If the dead man switch is not working it's a system malfunction.

That might be technically true, but it's irrelevant. Nowhere does Tesla ever describe it to the customer as a dead man switch.

And it wasn't malfunctioning. He wasn't a dead man. He was very much alive, understood the warnings, understood that the car expected him to keep his hands on the wheel and keep paying attention to the road. He understood the warnings so well that he was capable of avoiding them with such proficiency that he did not receive one for 15 minutes.

It's driver responsibility to drive the car and pay attention to the road.

By representing the car to come with an auto driver, they implicitly take on that responsibility.

By naming it "Autopilot" they take on that responsibility.

Imagine a driver driving down a parkway at speed and thinking "I'm on a parkway, so I should shift the car into Park."

That's how dumb that argument is.

If a driver ignores the requirements of their driver license AND the vehicle's clearly worded warnings, then the driver is entirely responsible. Claiming that the driver is not at fault because they interpreted the word "autopilot" to mean "I can disregard my responsibility as a driver and ignore the vehicle's very clear warnings" is absurd.