Ah! You probably didn't read my first reply on the subject (why should you, this thread has gotten quite long) . . . The Universe is ~12-15 Billion y/o, and life on this planet is supposed to be 3-4. Assuming an infinite universe we many Earthlike planets orbiting earthlike suns, you'd figure the odds are at the very least 3 or 4 civilizations developed such as us in the Universe - probably more.
So, if you're using this as your starting point, and also trying to explain why we haven't seen ET's (I know, I know, many on this thread say we already have) because they want to leave us alone, one has toalso assume they have a similar moral or ethic as we do to make the decision to leave us alone. Hell, if I were an intelligent alien race, I'd erase humans from the universe and move in, so it's probably a good thing I'm on our side.