Stephen Hawking suggests not to contact the aliens

Stephen Hawking suggests not to contact the aliens. He said to the BBC: "We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet." http://news.bbc.co.uk/2/hi/uk_news/8642558.stm
However is there a choice? Maybe we should prepare ourselves for the contact with these extraterrestrials especially since also Hawking said that it is realistic to believe in alien beings.