If, as I understood, Nefario disrespected the company rules, and therefore its owners, when he closed down GLBSE, it doesn't make sense to attribute such closure to GLBSE (= its owners), since, for all the matters, Nefario was no longer acting within his role of CEO. He was "attacking" GLBSE.
Until and unless someone authorize to represent GLBSE actually makes this argument on behalf of GLBSE, I wouldn't credit it.
So, it doesn't seem to make sense to me to give the other owners a scammer tag. Actually, I still don't think Nefario should have gotten it, since he was likely the victim of a threat, but that's yet another topic.
If so, he has to say so.
You can't prospectively refute every argument that might be made. You just have to make a case and then the other side has to choose what defense it's going to take. Otherwise, you wind up with an infinite burden of proof. Even if there's a good explanation, the people who are presently losing money deserve to hear that explanation from the people they trusted.
Scammer tags are provisional. They can be removed if new evidence appears. If someone doesn't pay you money they owe you and posts no explanation, we can give them a scammer tag even though they might have gotten hit by a bus. If we find out two weeks later they got hit by a bus and they make payments as soon as they can, we can remove the scammer tag and apologize. Scammer tags are more like warnings than findings of guilt.