No,there's good sense in what he says....

Look at it this way, (making the assumption that there is techinically advanceed intelligent life out there and it is contactable), every civilisation that has come in contact with a more technically advanced civilisation on this planet has had the shit beat out of them.

Chances are that if there are beings of this sort roaming around out there, then they're likely to be far more advanced than we are. That's bad news.

Didn't you see "War Of The Worlds"? You know, two hours of Dakota Fanning screaming at the top of her lungs? A simple rhinovirus will kill them.

Fageddabouttit...

Hawkings makes sense with his comparison to the Columbus landing in the Americas thing. Zoomie has the right idea too about disease.
The danger of contact with aliens would be novel and horrible diseases. If they can reach us then they will more likely establish missions/outposts/consulates here than we would at their home planet. Thus like Columbus in the Americas we'd be the ones most likely to die out completely.

This is what happens when the producers of V ignore their fan mail.

Didn't you see "War Of The Worlds"? You know, two hours of Dakota Fanning screaming at the top of her lungs? A simple rhinovirus will kill them.

Fageddabouttit...

Did you see her in The Runaways?  Two hours of her snorting rails and lesbo action. 

I got the foot thing, not the kid thing. She's 15 and I have daughters. Gross, Sash.

Interesting though ...