Yeh, Yeh, Yeh, I know. I've heard this a hundred times. Unless we do XYZ mankind will be DESTROYED!
Why should I worry about something that may or may not happen a thousand years from now?
Excellent point, along with all of the other ones in this thread.
It may be necessary to point out that Hawking is trying to establish a career transition from physics theoretician / mathematician to pop-star.
Physicist Michio Kaku made that same jump years ago. Isaac Azimov (a former chemist) and former astronomer Carl Sagan were among the first.
Physics and science require adherence to strictly rational discourse. Pop-stardom is about getting attention for yourself to promote "exposure" and "brand value". Like a porn star or chewing gum.
Hawking has been making grossly self-contradictory statements for a long time now, (coincidentally concurrent with the termination of any more publishing of scientific articles or papers). He first warned against trying to contact ETs (calling the SETI program foolish) then reversed himself 180 degrees when a billionaire offered him a lot of money (and publicity) to join SETI.
He was once a scientist and worthy of great attention. Now he is just another clown without make-up, hustling for website hits and Fecesbook followers.