I believe in freedom of speech as long as it is not hateful or personal, so on that basis I have left it, though I'm not saying I am correct. Other members tell me if I should hit delete or let it run.
I've got a lot of respect for your position on this, Simon.
When even the likes of Facebook, Youtube etc are pulling posts/videos/stories then it's quite clear that free speech is under threat, and even the most staunch defenders of this are apparently getting a bit nervous and caving in without court orders, which is somewhat unprecedented (a bit like everything in the last few months!). Albeit this is perhaps for their own purposes - a pragmatist would argue that the position of the web giants is one that is necessary for their business models to be feasible without employing millions of people to "fact check", and the reality of the position at the moment is such that they (a) need to keep their business viable and (b) avoid engendering lots of hostility from their products, sorry, I think I meant from their "customers" 
To be completely honest, I am rather surprised to see this thread spring up here, and I'd been reticent to comment in it, in part on the basis that adding one more voice to the otherwise near-unanimous chorus against the hoax idea seemed like it would accomplish very little. It does seem rather at odds with the rest of the tone, and calibre of information and discussion elsewhere on the site.
I'd also be concerned that IFSQN's credibility amongst non-members could have a detrimental effect elsewhere. I see it in the same way as the anti-vax lobby, to an extent - if I am searching for justification for my scientifically questionable (at best) viewpoint, and I stumble across a source that is reputable and full of apparently knowledgeable people, I may take information from there as having considerable weight in supporting my view, even if this information is scattered amongst lots of more rational counterarguments. Is there therefore a risk that other people might stumble across this and consider it a credible source of information to support a fringe view on otherwise well-established science? Seems possible...
Obviously this then raise the question as to whether websites have a moral obligation to protect the public from their own lack of knowledge (or outright stupidity, in some cases), and does that outweigh the individual's obligation to take responsibility for their own actions? Only IFSQN can make this decision about where their site sits in this argument. I don't envy them that decision, as there probably isn't a right answer!
I'm a big supporter of personal freedoms, and believe that everyone should have the absolute maximum possible freedom to do anything they wish, as long as it does not cause detriment to the wellbeing of others. This is where I see the issue here being more complex, as ignoring the advice on Covid19 is an exceptionally selfish act - we should be free to take risks of our own, that only affect us, but it is demonstrably the case here that if I choose to ignore the advice, the risk being taken is potentially very much at the expense of others.
I will say that it is a jarring to see such derisible "science" appear here. With the greatest respect to Glenn, who has spent many hours sharing his considerable expertise on auditing and FSMS systems, the stuff about viral transmission is abject nonsense. Given that viral transmission via food is something that at least some of us need to be concerned about as part of our profession (see e.g. norovirus, Hep A etc), it does seem particularly incongruous - really it's not that far removed from claiming that I don't believe in Salmonella transmission by food, and therefore stating that people don't need to cook chicken before eating it - such a statement could perhaps been seen to slightly lower the credibility of the forum. It wouldn't affect my use of it, but I've been doing this long enough to have a reasonable sense for what is credible and what isn't, and I'll go and cross-check "facts" anyway. Might have a different impact on those starting out their careers though.
One option that might give a best-of-both (or least worst?
) approach to the dilemma could be adjusting the visibility of the off topic section? I've no idea if your underlying forum software supports it, but I use a music forum where the off-topic section is not publicly visible; it's only accessible to members who are logged in. This would allow the discussion to continue (the merits of which are perhaps a separate question), but at least pull it out of the publicly visible part of the site.
The other option would be to consider where the thread is going and if it actually serves any purpose. I've seen other forums take the view that their purpose is x, and as the discussion at hand isn't about x then it's entirely reasonable to delete a thread. Again it's your call whether to apply that here, but do any of us think that this discussion is going somewhere?