It's just scare tactics, propoganda.
The aliens are really our friends, but the corrupt moguls are trying to make us afraid of them so they can continue to fund their bloated, military industrial complex, by getting us all geared up for a classic, pre-emptive strike.
I've had many private conversations with these supposedly dangerous aliens, and if there's one thing I've learned it's that they think we're a silly bunch - and that they're completely willing to leave us alone.
Well... one night, Voltrab did let it slip that they might destroy us in a blink if we ever discover the ability to form hyper proto-plasma fusion matrices. But there was a little
influencing the conversation, so I just thought it was the leaf talking.