Dangerous to itself. Highly auto-toxic memes are usually self-limiting because they promote the destruction of their hosts (such as the Jim Jones meme; any military indoctrination meme-complex; any "martyrdom" meme). (GMG) (See exo-toxic.)
Any attempt to hinder the spread of a meme by eliminating its vectors. Hence, censorship is analogous to attempts to halt diseases by spraying insecticides. Censorship can never fully kill off an offensive meme, and may actually help to promote the meme's most virulent strain, while killing off milder forms.
and my personal favorite:
"A tune or melody which infects a population rapidly." (Rheingold); a hit song. (Such as: "Don't Worry, Be Happy".) (f. German, ohrwurm=earworm.)
Read them all, and then try to get the ideas out of your head.