This stuff is fascinating, looked at in the context of the current political discourse about truth.
I cannot help but be somewhat suspicious. Not of Fisk, necessarily (I haven't read anything on this by him), but more of the 'anti-warmonger' attitudes of those who seek news of Western duplicity. Primarily because the people offering that narrative are genuine warmongers, and have been bombing all over Syria for years, and have just taken selected journalists around the site in question (selective access is not new, but is it innocent in this case? If so, why?). None of that means in and of itself anything re: the veracity of the chemical weapon claims, but it does put the response of people here into an odd light, imo. The 'Stop the War' impulse is built on a rejection of perceived imperialist aggression, and to bolster itself, it draws succour from people who live by imperialist aggression - just they happen to be further away. Then there's the weird moral dimension: chemical attacks are faked (to justify a tokenistic gesture that has done nothing), but the barrel bombs fall [but this is Wiki and therefore editable by anyone and therefore it means nothing!] and eh, whatever.
Again, none of that means anything for the 'facts of the case', necessarily, but it does mean I am instantly more cautious. Am also curious as to the burden of proof - if the Russians say it was staged, they have to prove that via affirmation, not absence and inference built on mistrust.
Ramble: it strikes me that the performance of scepticism is VERY distinct from the act of scepticism. The pervasive doubt puts people into corners where they want to be sceptical, but often end up being cynical, or are less generous with their scepticism, or, when faced with a more conscious examination of the unknowability of the world, despair/realise their own inescapable ignorance, or flip the locus of their scepticism from one source of half-truth to a source of un-truth.