There has been a resurgence in the world of science, in the hunt for extraterrestrial life. Articles are appearing everywhere. One article complains that the conversion from analogue to digital transmission means the aliens can't find us any more. We aren't broadcasting on a wide range of frequencies now. Well, that might not be a bad thing because there's also speculation that any aliens who do visit might not be friendly. An open-house policy might not be the best policy.
"We might like to assume that if there is intelligent life out there it is wise and benevolent, but of course we have no evidence for this. "
Why would anyone assume that? Look around at the dominant species here. Wise and benevolent? I think not, overall, and any alien assuming that of us would be in for a very unpleasant surpirse.
Perhaps the aliens will simply move in and take all the oil, coal and gold. Would we do it to them? Yes. Immediately after we tried to buy their planet with some shiny beads. If there are aliens and if they are benevolent and trusting, they'll rue the day they met the human race.
Even the Royal Society is taking the idea of alien life seriously now. They've always considered it all 'woo' but no longer, it seems. Well, when a venerable scientific institution decides to look at something that's only in the realms of possibility at this stage, there is hope for science in general.
I have my own ideas of why aliens don't visit us or transmit to us. Look at how we treat people of our own species who are different. You don't even need to go as far as racism or sexism. Too fat, too thin, too tall, too short, likes a smoke, likes a drink, drives the wrong kind of car, has the wrong accent, believes something different, votes for the wrong politician and so on. We are nasty to each other because of differences an alien race wouldn't even be able to detect.
What would they imagine we'd do to them, an entirely different species?
Maybe they are receiving our transmissions and thinking 'Look out, it's the humans! Hide!' Who could blame them?