Apropos of nothing, one theme I've noticed having viewed this debate over a few years is that the helmet wearers always seem to be tolerant of both camps, wheareas the anti-helmet guys appear to be more militant and confrontational. Sneering references to "plastic hat wearers" are very common, but the opposite (I'm guessing a comparably sneering opposite might be "bareheads", or "bandana wearers", "cap fans" or whatever, it's hard to find an example) seem to be entirely absent.
I'm not sure why you think those would be the opposites - helmet zealots tend to call non-users "organ donors", "brain-dead" or just general terms of abuse like "tosser" and hoping that we die by smashing our heads into a flat smooth piece of road (not a stone because then a helmet wouldn't save us).
It does seem closer to 50-50 in this discussion, but a lot of the worst insults used to get deleted and now this thread is pre-moderated, they don't even appear or get emailed out. I feel the confrontational stuff that survives tends to be anti-helmet because it contains some facts, whereas a lot of the pro-helmet posts used to be just abuse - at best, they're emotional and anecdotal, which is difficult to be confrontational with, because if someone challenges an anecdote, all the story-teller can say is claim "it really really happened honest".
Anyway, for a more realistic sample of the abuse, try advancing an anti-helmet or even helmet-sceptic view in an unmoderated facebook discussion (on some page/group not full of your friends) and see how long it takes before you get death threats!
The aggression and insults In Real Life are almost all one-way traffic from helmet zealots towards non-users, to the point of banning us from trying to ride with them on open public roads sometimes.