Do you have a disagreement besides fairly stupid rhetoric? The lack of alternatives is genuinely evidence against SI's cause, whereas presence of alternatives would genuinely make it unlikely that either of them is necessary. Yep, it's very curious, and very inconvenient for you. The logic is sometimes impeccably against what you like. Without some seriously solid evidence in favour of SI, it is a Pascalian wager as the chance of SI making a difference is small.
I'll rephrase: your argument from alternatives is as much bullshit as invoking Dunning-Kruger. Both an argument and its opposite cannot lead to the same conclusion unless the argument is completely irrelevant to the conclusion. If alternatives matter at all, there must be some number of alternatives which reflect better on SI than the other numbers.
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.