Hawking has said that we need only look at the history of inter-species relationships on our planet (let alone race relationships) to get a hint of what exopolitics might look like. He goes on to mention that in terms of the search for alien life, we'd do best to keep our heads low.
I'd rather compare alien encounter with something like Marco Polo going to China: he didn't wish to kill them all, was impressed by some achievement and inventions but was also disgusted by the Chinese diet. Came back and wrote a book, and it was so foreign most readers didn't believe him.
And there is a reason to believe that they probably won't be - they will be the product of Darwinian evolution, just like us, which is really not a very nice thing.