But this is actually a much less likely alternative proposal than you seem to think. You seem to be implying that “deciding to send out probes” is something like “having five fingers on your hand” – it’s a one-off decision that’s common across an entire species for the whole of its existence.
And it is indeed silly and self centred and so forth to say “humans have five fingers, therefore all intelligent species will have five fingers”.

But actually “sending out probes” is in a list that includes “wearing hats” and “driving steam-powered cars” as well as “building pyramids”. It’s something that some members of a species might do at some point. And it’s a massive assumption that no members of a species will ever decide to do that at any point in their history. Look at our own history; look at the massive variety of cultures and activities that humans have had, and we’re only at the dawn of human history. Are we really all so similar that an idea that a French farmer in 1950 would reject as stupid and pointless would definitely also be rejected by a Japanese nobleman in 200 AD or a Sumerian merchant in 2500 BC or a New Yorker in 3500 AD?

Would you really be prepared to bet that there’s a single alien species that will _never_ build a pyramid? That in the, I don’t know, five million years from the first Vogon striking sparks from a rock, to the climax of interplanetary Vogon civilisation and on to its inevitable decline and extinction from a disease contracted from a dirty telephone, no Vogon of the trillions of Vogons who have lived will ever make or even consider making a building that’s smaller at the top than it is at the bottom? A culture doesn’t reject ideas on a once-only basis.

So this is another value of keeping a speculative wariness about anthropocentric assumptions re: extraterrestrial life alive–it may help make us more alert to some similarly limiting “centrisms” in our thinking about the contemporary world.

But I think you are too quick to stake out a pragmatic ground and defend it as the only choice, both in terms of public policy and in terms of a research agenda that doesn’t have a particular policy objective.

It’s true that pursuing SETI at any scale requires a kind of paring off of the possibilities that we simply can’t deal with within that framework, including the possibility that there are many intelligences in our galaxy but that almost none of them have technological infrastructures that signal to us in ways we can hear, or that almost none of them would ever want to. But it is possible, as Paul Davies’ recent book observes, that the overly quick paring down of SETI to the most convenient assumptions might miss both the classic side benefits of any kind of basic research (e.g., that trying to think more broadly and creatively about the problem might fetch up some other application that no one was aiming for in the first place) and might lead us to miss out on some feasible approaches to imagining and detecting extraterrestrial information transmission from technological infrastructures or biological intelligences very unlike our own.

Second, I really contest the idea that speculative thinking has no value in its own right unless it can match to publically sustainable, practical research programs. This is a classic, repeated problem in modern science itself: researchers who are pushing well outside of the tools and knowledge base of the moment to engage in speculative thinking are scorned by colleagues for their extravagant and impractical visions until suddenly it turns out that they were really on to something. This is all the more the important now–we have striking new ways to collaborate and collate speculative thinking at the same time that the logics governing financial support are driving away from basic science.

Third, a somewhat separate point: I really dislike the general proposition that scientists or other scholars have to ‘trick the public’ by continuing to serve up simplified findings that they believe work well within existing public understandings in order to gain support for worthy public projects. After fifty years of that kind of logic repeatedly blowing up in the face of scientific and technological projects, it’s time to think differently about building sustained coalitions to support scientifically-driven public policy.

So why are we paying attention to a “study” regurgitating 50 year old ideas? Is it because the people conducting the study are so ignorant? I doubt it actually. So the third point that strikes me is that THE PUBLIC IS VERY DUMB. Or, if you prefer, that the “audience” for extrabiology keeps changing as the population ages, and that newcomers begin with very little knowledge. Most people think they’re being quite sophisticated by considering the possibility of sentient beings such as Vulcans and Romulans and Ferengi. Granting “humanity”, even in theory, to something looking like a bowling ball which thinks deep philosophical thoughts in isolation from its fellows over a lifespan of millennia would be a bit of a stretch. So the paper quoted in io9 is aimed at ordinary humans rather than working exobiologists.

The fourth point is that after you’ve properly considered all the possible variations in alien species and the many different paths towards civilization or some sort of knowledge that such beings might have followed, you’re kind of at a dead end.

Imagine Sagan and Morison having a meeting with Lyndon Johnson in the late 1960’s to tell him that aliens might dwell elsewhere in the galaxy, and might even be exploring our solar system with their version of NASA. “What do you want me to do?” LBJ might have asked. “Will they be friendly or hostile? Will they side with us in Viet Nam? Can they talk to Congress about passing an education bill? Can they give us a cure for cancer? What will they want in return?” And if you are Carl Sagan, and think it’s just absolutely wonderful that we can almost prove mathematically that intelligent alien species are spread across the galaxy and that this almost-a-fact is so exciting it needs to be proclaimed to everyone, what would you tell LBJ?

So yeah, all kinds of things may be possible in space. But that’s not useful knowledge. And I think in the end, we just have to shrug and tell ourselves that in a thousand years when we’ve got faster than light spaceships and a lot of money we’ll go looking for the really interesting aliens, but right now we have to settle for detecting messages from aliens who think something like us, and communicate their thoughts sort of as we do, with technology that we can understand. Yeah, it’s “anthropomorohic” and even our grad students can see we’re being embarrassingly simple-minded, but realistically what other choice do we have?