In part 5, Luke gives humanity a 5% chance of surviving this century.

He says of machine intelligence "by default it will be disasterous for humanity".

"By default", a 747 is a pile of scrap. "By default" no aeroplane ever flies. This kind of arguing "by default" just seems to be being used to introduce nonsense into the conversation while making it sound reasonable.

I think this line of argument needs to become uncool. If the best someone has is an argument "by default", then that just indicates that they don't know much about the history of engineering safety, which surely provides a vastly better basis for predicting the success rate of future safety-critical engineering projects, than the whole "by default" line of argument.