Now: I saw that same article, and I think Dr. Hawking was being speculative. He seems to have based his statement upon extrapolation of what happened here, in human history, when technologically advanced cultures came into contact with those which were less so.

I would argue his point because he seems to be denying any possibility of cultural evolution: that a culture's ethos could not evolve to a state wherein it's not okay to pick on the primitives.

Yes, as a species we've had a great deal of trouble with that one. We're still trying.

But there's no reason to think an alien culture wouldn't have more success.

To sum up: yeah, aliens might turn out to be big jerks. Or they might turn out to be really cool guys. It might even turn out that we're the only sentient life around, though that would be pretty surprising.

We are (a) and (b) but not (c). I think that other civilizations probably exist out there, but I also think that we will never, ever, see them, simply because of the distances between the stars.

The fastest spacecraft to ever leave the solar system is currently Voyager 1, which is travelling at 62,100 km/h. The closest star is Proxima Centauri, at 4.2 light years, or 3.97342193 × 10¹³ kilometers. At that rate it would take approximately 6.4 x 10⁸ hours, or about 73,000 years to get that far away (and it's not headed for Proxima Centauri).

The calculation for determining the odds of a technological civilization is known as the "Drake Equation"… but most of the numbers are unknown.