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.
Hyroglyphx writes: To concede that you shouldn't look for something on the pretense that it could be dangerous would preclude all of science to cease and desist on that exact same basis.
I took Hawking's point to be that we should not be trying to make it easier for them to find us (by setting up beacons). I don't have a problem with searching for life elsewhere, though I think SETI is a rather dubious way of doing that.