jaybear brings up an interesting point in this thread (and please don't revive it; pretend I'm discussing a possible issue and prevention, rather than repercussions), regarding the effectiveness of the volunteer system in such instances. While I don't agree that volunteerism has necessarily failed, I think this might indicate a certain need for the refinement of the support system (and it's going here instead of suggestions since it has a definite impact on the community).
I have two suggestions to solve this. First, make a person have an LJ for, say, a month before being able to post to support. This would allow them to get the general "feel" of the community; Slashdot does this sort of thing with moderation, and while I hardly want to base this site on Slashdot's model, I think it's a good idea. Secondly, there should be a way to ban people from the support system who have shown a tendency to be abusive, the same way you can ban people from journals. (This may be in place already and I just don't know about it.) A similar idea might be some kind of acknowledgement from someone authorized to answer support before you can, but I think would be too restrictive.