To answer your second sentence on, one consideration is that it is highly questionable whether scanning and uploading is even possible in any practical sense, as people who actually work with brain preservation on a daily basis and would love to be able to extract state from the preserved material seem to consider the matter: It's "possible" philosophically, but not at all practically. This suggests that it's low enough feasibility at present that even paying serious attention to it may be a waste of time of the "Pascal's scam" form described in the linked post (whether the word "scam" is fair or not).
The upload thread talks about the difficulties in making an upload of a single specific adult human, which would have the acquired memories and skills from the biological human reproduced exactly. (Admittedly, "an upload of John von Neumann", taken literally, is exactly this.) A neuromorphic AI that skips the problem of engineering a general intelligence by copying the general structure of the human brain and running it in emulation doesn't need to be based on any specific person, though, just a general really very good understanding of the human...
Nick Szabo on acting on extremely long odds with claimed high payoffs:
Beware of what I call Pascal's scams: movements or belief systems that ask you to hope for or worry about very improbable outcomes that could have very large positive or negative consequences. (The name comes of course from the infinite-reward Wager proposed by Pascal: these days the large-but-finite versions are far more pernicious). Naive expected value reasoning implies that they are worth the effort: if the odds are 1 in 1,000 that I could win $1 billion, and I am risk and time neutral, then I should expend up to nearly $1 million dollars worth of effort to gain this boon. The problems with these beliefs tend to be at least threefold, all stemming from the general uncertainty, i.e. the poor information or lack of information, from which we abstracted the low probability estimate in the first place: because in the messy real world the low probability estimate is almost always due to low or poor evidence rather than being a lottery with well-defined odds.
Nick clarifies in the comments that he is indeed talking about singularitarians, including his GMU colleague Robin Hanson. This post appears to revisit a comment on an earlier post:
In other words, just because one comes up with quasi-plausible catastrophic scenarios does not put the burden of proof on the skeptics to debunk them or else cough up substantial funds to supposedly combat these alleged threats.