Of course, there's something to be said for the hunter, "Seeing you, before you see me."

Also, while the remaining silent (unresponsive) theory may have some merit, the inevitable flaw in it's logic is that most civilizations will inevitably go through a decades-long phase where they broadcast their positions inadvertently - as they discover radio communications. The earth certainly did. Even if we ceased all airborne transmissions today, there is a bubble of radio communications slowly expanding out from Earth that will continue for centuries. So, while the civilizations may choose to remain unresponsive to queries, they certainly failed to remain "hidden."

Finally, it is pointlessly assumptive to speculate on how an alien species would morally adjudicate us. "Alas", they may say, "look how atrociously they tended their planet!" Of course, a competing theory is that our terrible stewardship may be the evolutionary norm. A sentient species, as they grow in awareness, inevitably destroys their homeworld - after which they either die off, fix the planet, or move spaceward.

But since we are the only sentient species we are aware of, we have a study size of "one." :D