This is exactly the point why I will never understand people in US and the sort of thing with labels and warnings. You don't microwave a cat just because there is no warning label saying you cannot do that. You do not dry your hair submerged in a bath just because there's no warning label. And knowing how imperfect and faulty this system is (which is what the family says the driver told them), I would avoid engaging Autopilot at all costs even if Tesla had no warnings and instead praised this feature as being the safest.
Unless you absolutely have to (in case with a doctor), you do not outsource the life-threatening decisions to someone else. If you're tired and cannot drive, park and have a rest instead of watching movies while driving on Autopilot.
What I'm trying to say is that in the end it's your decision, and you have to live with the consequences.