Aliens exist, and they may be out to get you — or so says legendary astrophysicist Stephen Hawking, who cautions that attempting to contact E.T.s could result in humanity's total annihilation. "If aliens ever visit us," says Hawking, "I think the outcome would be much as when Christopher Columbus first landed in America. Which didn’t turn out very well for the Native Americans." Are Contact-style programs to reach out across the stars putting our world at risk? (Watch a Fox report about Stephen Hawking's alien claims)

Fortunately, most ETs are probably too dumb to kill us: Since "Hawking theorizes that most life would be microbial," says Jack Loftus in Gizmodo, death by alien invasion is only "the worst case scenario" — at least "so long as deep space's version of microbiology doesn't have access to a death ray."
"Stephen Hawking's tips for contacting E.T: Everyone please just STFU"

Trying to hide just makes us look silly: To borrow the insight of Arthur Clarke, any alien race capable of traveling between stars is going to be so advanced their powers will seem "magical" to us, says Razib Khan at Discover. "I doubt anything we do will matter either way (i.e., I don’t think we could hide, or, get their attention)."
"The aliens are out to get us!"

Perhaps they will come in peace: Hawking has "previously spoken in favor of human colonization of other planets, arguing it would ensure" the survival of species, says Rebecca Boyle at Popular Science. So, why should we assume that "aliens with the same motivations would probably not be trustworthy"?
"Aliens exist, and we should avoid them..."

Take Hawking with a grain of space dust: His warning "is undeniably true," says Daniel W. Drezner in Foreign Policy. "But dare I say that Hawking is being a bit simplistic? Oh, hell, who am I kidding, I'm a blogger. Of course I'll say that Hawking is being simplistic."
"How do you say 'realpolitik' in Klingon?"

http://theweek.com/articles/494934/stephen-hawking-dont-talk-aliens