I admit, my first sentence was in poor taste. Apologies to Andrej.

At the same time, saying that something isn't possible to prove when we literally have no idea about its provability isn't a good stance for a researcher to take.

This is similar to my problem with the list of AI researchers you've provided. Saying that there is nothing to fear and waving your hands isn't exactly scientific.

Also, it isn't like these people (Sam, Musk, etc) literally think it could happen any day. The point is that we should be aware of the risk and prepare accordingly -- why is that unreasonable?