I agree with Hawking on this.
I wonder why he is coming out with it now, rather than say 20 years ago. But then maybe nobody asked him 20 years ago.
I do agree with the point that such an alien nation could be expected to be advanced. Perhaps that would be comparable to an advanced nation such USA which invaded Iraq on a whim in 2003 and caused much damage and death.
There is no reason that an advanced alien civilization would not see us as something like ants to be crushed.