Arthur, I guess that would assume that we are more advanced than any discovered intelligent life. But, what if we weren't? That would give us some serious reason to reevaluate. And the discover of any intelligent life, would imply that there was more, and that it was inevitable that some of those more would be more advanced than we were.
It would also mean that if we destroyed ourselves, then - so what? We would know with absolute certainty that all we were was a bit of genetic diversity, and look at how we scorn that.