2. There is no spike protein anyone knows of which would have been used in this research
3. The PRRAR furin cleavage site is not one humans would have tried it is unlike any other known furin cleavage sites in coronaviruses
4. There are now many known related sarbecoviruses which have been found with furin cleavage sites
5. Furin cleavage sites have independently evolved in multiple different branches of coronaviruses, probably a dozen times that we know of now.
6. The furin cleavage site is short and can easily happen through recombination with another virus due to coinfection.
7. This is very likely what happened due to infection with the SARS-CoV-2 ancestor and an HKU9-like virus.
It is not particularly suspicious that the thing which we were worried about happening and causing a zoonotic spillover event is the thing which actually happened.
They were going to experiment with multiple backbones, experimenting with multiple variations of spikes, looking specifically to try novel types of furin cleavage sites.
There was no public reporting of what happened with this research. We don't know what they have because WIV database was taken offline. They claimed to have searched it, but what they claimed was the closest match in the database was not, in fact, as close as a sequence they had published. Given that demonstrable lie, there is no way to verify any claim about what sequences were or were not known and possibly involved in this research.
Furthermore the person who submitted the proposal was also the person who broke ethical standards to preemptively shut down all discussion of a human release.
That isn't to take away from the possibility of a natural spillover. The facts that you say about that are facts. But accidental release is also possible. And the lack of transparency from those who are most likely to have made the mistake heightens suspicions, it does not lessen them.
It is research that "sounds like" what happened with the SARS-CoV-2 zoonotic spillover, but that isn't a strange coincidence. They were researching the thing they were worried about happening, and then it happened. Their research proposals naturally rhyme with what actually occurred because they had studied and understood the problem enough to guess more or less accurately what the process would be. There are still massive gaps in between this proposal and SARS-CoV-2 that you could fly a plane through.
"The grant proposal very specifically is concerned with using the WIV1 and SHC014 backbones, nothing related to SARS-CoV-2." The counterargument is "Well, they could have altered the proposal when they pursued funding elsewhere." The takeaway is that it is not likely this specific proposal was funded elsewhere, leading to SARS-CoV-2.
"If they actually carried out the research in this grant proposal you don't get from there to SARS-CoV-2, those are all SARS-1-like." I do not personally know how to evaluate the accuracy of this claim, but if true, it resonates with the first claim: this proposal funded elsewhere would not lead to SARS-CoV-2.
The argument claims about it being hard/expensive I think are less compelling, as there is a lead time of several years with experts in field performing research. A more compelling version of this argument would look like (completely making up numbers): "On average, it takes 4.5 years to develop the first samples of a novel virus using a selected backbone, CRISPR technology, and gain-of-function culturing. Therefore, even if this research was funded in 2018 we would not expect it to have led to SARS-CoV-2". I'm not saying that argument is accurate at all, just saying it's more specific than "it's difficult".
The argument claims about the evidence being missing I think isn't going to be motivating for a person who has a reasonable expectation that secret research is done and does not have trust in government transparency (either US, China, or otherwise). I'm not making a point here that evidence isn't needed (far from it, evidence IS needed). I'm evaluating from a polemic perspective what kinds of claims and arguments are useful for advancing the conversation with someone who holding a dissonant viewpoint.
Thank you by the way for making specific claims that can be fact checked such as the two referenced at the top of this comment.
That sounds like a very tenuous line of reasoning to me. Almost like saying "We know that Mr. A proposed shooting Mr. B, so let's reconsider that Mr C. may have stabbed Mr. D."