I have to disagree completely here. In the case of going to the moon, the most reasonable prior for "astronauts pick something up that then returns with them intact and is able to survive in highly oxidizing atmosphere" should be near zero. The prior for "we bring something to the Moon that somehow contaminates the place" should be significantly higher than that, yet still very small. This is, of course, taking into account that we didn't know how hardy tardigrades and some of the various types of extremophiles could be then. But, IMO, I still don't think that should raise the risk estimate of bringing anything back very much, nor should it raise the risk estimate for contaminating the place to anything approaching that of any of the very real possibilities for which NASA literally had 8+ contingency plans. And I say all that even while factoring in that the potential impact of bringing something back that would be able to survive could be the destruction of humanity, destruction of Earth's biosphere (and all of humanity with it), or any of a number of other existential risk scenarios.

With AI, those probabilities are all flipped on their heads. The reason we know of some of the risks, e.g. the risk of deep fakes being used as tools for fraud, is because they have already happened. That one single scenario alone having already come to fruition takes whatever anyone should have for a prior probability of said risk and shoots it straight up to 100%. And, that alone is a key difference between AI today and lunar or terrestrial contamination by alien life in the 1960s.

Let us not also forget that there are many, many other risk scenarios than deepfakes being used for fraudulent purposes. Much as I hate to reference Rumsfeld on this, there truly are "unknown unknowns" here, and we have to take that seriously. And then there are the middle ground scenarios, such as the possibility of severe and lasting economic disruption, to the point where capitalism might not be able to function as it has for the past several centuries. I truly don't believe that any foreseeable "internal" risk[0] could cause capitalism to completely stop working forever, unless we just run out of stuff to dig up out of the dirt, but AI certainly could cause multiple decades of disruption, which would be nearly as bad for most people alive today.

I'm gonna cut myself off there, because I think this is getting a little ponderous, but also because I think my point is made now: biotic contamination, whether forward or reverse, involved a sum of a lot of hypotheticals with very low probabilities, whereas AI risk involves a sum of some certainties, a few potential (though perhaps low probability) existential risks, and also an indeterminate number of unknown risks of unknown probability. It seems pretty clear once you crunch it all out that AI is certainly the greater threat.

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[0] Mmeaning one that originates within capitalism itself, like AI, rather than one that originates outside of capitalism, but puts pressure on the system, like climate change..