He said what?? (*Facepalm*)
This is why I put him on ignore. Not saying you should, Almond; I'm only pointing out that MM's uneducatable, and refuses to think his way through responses. He only posts to be argumentative, nothing more.
For you, Almond, or anyone else who's curious: Greening discussed the liberation of reductive species in the plethora of burning materials; for example, the PVC that would also be present in the building could also have released corrosive chemical species - HCl, or even Cl2 - that could've contributed to the corrosion noted, as well as released sulfur itself. You, of course, know that when someone like Greening posits individual chemical reactions to make his argument, he's not saying that they're the only ones occuring; rather, all he's saying is that they're illustrating the point that he's trying to make.
And yes, agreed: Sulfur dioxide is indeed painfully corrosive to steel period, let alone at the temperatures seen in a structure fire. I mean, people are concerned about steel corrosion over time at normal outdoor temperatures from acid rain. Take that to a higher temperature state and you end up with elevated reaction kinetics. That's basic, freshman level chemistry.