The people for the most part are kooks, generally falling in the vegan, tree higger, new age fringe. I have been surpised to see how many from the other side of the aisle also share the nutty paranoid and ignorant views.
This thread for example, is perfect. The things former lurker is saying are ignorant, meaning he has no idea what he is talking about or the science he ostensibly is commenting on.
Fringe and tin foil arguments are also of this nature.
I now have seen at least two posts of this nature meant to disseminate these ognorant fear mongering misinformation.
This sort of post also is harmful in that it moves the debate away from rational examination of specific vaccines or issues surrounding them. In your example, for example, if this thread is representative of the argument, no one would take it seriously.
Now I'm surprised you didn't toss in left-wing radical DU reading, UFO cult, anarchists in there. You sure know how to launch smear attacks. That's about ALL you know however.