Ok, if what you're saying is not "SI concludes this" but just that we don't really know what even the theoretical SI concludes, then I don't disagree with that and in fact have made similar points before. (See here and here.) I guess I give Eliezer and Luke more of a pass (i.e. don't criticize them heavily based on this) because it doesn't seem like any other proponent of algorithmic information theory (for example Schmidhuber or Hutter) realizes that Solomonoff Induction may not assign most posterior probability mass to "physics sim + location" type programs, or if they do realize it, choose not to point it out. That presentation you linked to earlier is a good example of this.
I believe that Hutter et all were rightfully careful not to expect something specific, i.e. not to expect it to not kill him, not to expect it to kill him, etc etc.
You would think that if Hutter thought there's a significant chance that AIXI would kill him, he would point that out prominently so people would prioritize working on this problem or at least keep it in mind as they try to build AIXI approximations. But instead he immediately encourages people to use AIXI as a model to build AIs (in A Monte Carlo AIXI Approximation for example) without mentioning any potential dangers.
Those are questions to be, at last, formally approached.
Before you formally approach a problem (by that I assume you mean try to formally prove it one way or another), you have to think that the problem is important enough. How can we decide that, except by using intuition and heuristic/informal arguments? And in this case it seems likely that a proof would be too hard to do (AIXI is uncomputable after all) so intuition and heuristic/informal arguments may be the only things we're left with.
My friend, hearing me recount tales of LessWrong, recently asked me if I thought it was simply a coincidence that so many LessWrong rationality nerds cared so much about creating Friendly AI. "If Eliezer had simply been obsessed by saving the world from asteroids, would they all be focused on that?"
Obviously one possibility (the inside view) is simply that rationality compels you to focus on FAI. But if we take the outside view for a second, it does seem like FAI has a special attraction for armchair rationalists: it's the rare heroic act that can be accomplished without ever confronting reality.
After all, if you want to save the planet from an asteroid, you have to do a lot of work! You have to build stuff and test it and just generally solve a lot of gritty engineering problems. But if you want to save the planet from AI, you can conveniently do the whole thing without getting out of bed.
Indeed, as the Tool AI debate as shown, SIAI types have withdrawn from reality even further. There are a lot of AI researchers who spend a lot of time building models, analyzing data, and generally solving a lot of gritty engineering problems all day. But the SIAI view conveniently says this is all very dangerous and that one shouldn't even begin to try implementing anything like an AI until one has perfectly solved all of the theoretical problems first.
Obviously this isn't any sort of proof that working on FAI is irrational, but it does seem awfully suspicious that people who really like to spend their time thinking about ideas have managed to persuade themselves that they can save the entire species from certain doom just by thinking about ideas.