[citation][nom]guanyu210379[/nom]Hawking said something like because humans are like that.Actually..who knows...perhaps we are the only ones who are aggressive and greedy..[/citation]
Believing in the golden-hearted alien makes for some interesting sci-fi (not to mention certain religious cults). But realistically, there is very little basis for it and it ultimately proves to be naive.
In nature, we have countless examples of the strong praying upon the weak. Yet, I can't think of a single example of a stronger species helping a weaker species (other than humans, but even that is a dubious example).
It is logical to assume that any species capable of interstellar travel is far more technologically advanced than we are. So right away WE would be the weaker species and totally at the mercy of any such visitors. If they are without mercy, then we're pretty much stuffed.
It is also logical to assume that every intelligent species will act first for their own self interest. So they may not be malevalent beings, but just acting in their own best interests and we may suffer for it. Really, about the best that we can hope for is for the aliens to have a sort of Prime Directive wherein they refuse to interfere with other races (especially inferiors races). In which case, there would be absolutely no reason to make contact with us. They would observe, but never reveal themselves or get involved.
The idea of benevolent, peace-loving aliens who just want to be our friends and maybe share their technology with us... that is, in all probability, pure fantasy. At best it is an extreme long-shot (and by that I mean, you'd have a better chance of winning the lottery several times in a row).
So, yes, I think Dr. Hawking is dead-on when he predicts that nothing good will come of attempting to contact any extra-terrestrial intellience.