I just ask a few simple questions, myself.
The first of such is "what can a being do on its own and what requires cooperation with fellow beings?". Does the creation of interstellar spaceships indicate a being more or less prone to cooperation than a less advanced species? If the being in question has developed vast and sometimes terrible technologies, what sort of nature is being revealed by the fact it is traversing the enormous distances between stars rather than blowing up its fellow beings?
If such an alien were to show up one day, the ONLY valid approach would be to treat it as friendly. If it wasn't friendly, game over for us. If it was friendly and our own xenophobia led to us being hostile, though, our loss. I dunno. I see it a bit like Pascals wager in regards to the existance of God in terms of the logic involved.