What makes you think they're going to accept a mass murdering species into their confederation? A mass murdering species that also thinks of itself as the supreme one in the universe of course... Nah, you wouldn't, so why would they? I mean they are the superior race if they are head of the galactic confederation, at least compared to us... Would you accept that? Hm... And since they watched how you treated the sub species surrounding you, how you got rid of them all, I guess, it would only be normal, logical, to treat you just the same Yeah Never occurred that, maybe, just maybe, we're being tested since thousands of years, to see how we handle ourselves, how we deal with the notion of inferior and superior species; do we get eaten alive be the inferiors or do we destroy them all in the name of our relative superiority? Furthermore, what if both options were deemed a dead end from the perspective of the so called aliens? You get destroyed then, you didn't have what it takes to survive, obviously, you destroy them all then... It's raising a different question; who's next?