Glad you dropped by to join the conversation, Henry. I have an alterego who's a moderator here, so one of my official duties is to play WalMart Greeter: Welcome.

I don't know if I can offer proof that you're wrong, but I think I can offer something of a ray of hope. You wrote

For strictly philosophical and emotional reasons, I would be delighted if anyone could convince me I was wrong.

Ya know what? All it really takes is for the other guys, the ETs, to feel the same way. If we're looking for an intelligence which, almost by definition, exhibits curiosity, a curious intelligence would, I think, experience an emotion we might recognize as hope; a bias to defy the odds in hopes of solving the mystery. They might be hoping to communicate just as much as you (and me), and they might be inclined to try despite the perceived odds. Just as I think we should.

To give it a veneer of sophistication, think of it in terms of game theory. One outcome is as you describe: Analysis of the odds leads to a rational decision to not try. But another outcome is to figure, nothing ventured, nothing gained (a curious intelligence will risk a lot to solve a mystery because of the perceived high payoff), and to suspect that the intelligence we're looking for will feel the same way. Seems almost like a variation of the Prisoner's Dilemma, in which a choice to take the less obvious path and cooperate having faith the other party will too, works out better than the perfectly reasonable logic of betrayal based on self-interest. If we define the search in terms of looking for other intelligences who share our desire to communicate, the odds look a lot better to me.

And given my theory about sociability as a component of sapience and technology development, I think gregariousness helps the odds. If they're as sociable as us, they'll want to talk. And talk and talk and talk and talk. That's why there's a HabitableZone.