I think internalized "misocycly" (hatred of cyclists) is a contributing factor.
When a certain group is not a "default" one, generalizations about that group are often made based on behaviour of a small handful of its representatives (usually ones that do something objectionable). Cyclists are not the default, therefore they will be judged more harshly and their poor behaviour generalized more readily to the whole cycling population. This post provides some morbid fascination with the parallels between cyclists, who are an oppressed road user group in North America, and groups opressed in the society at large.
Another possibility is that maybe I just need to go to bed. Tiiii-red. Strange ideas floating around my head. Except that the parallels are obvious, no really, aren't they?