Obscenity

Obscenity is a speech act or image which evokes disgust or revulsion in people, usually on moral grounds. Not surprisingly, it is liberals more than conservatives who favor legal protection of obscene images and words.

Words that express hatred are often obscene, with bathroom language eclipsed only by bedroom language. Words for urination typically express anger, while comments on low intelligence or integrity use words for defecation.

Scholars are at a loss to explain why the language of love is reserved for the deepest levels of hostility and hatred. "Effing this" (the thing I despise) or "F--- off" (go away, you) employ a metaphor for sexual intercourse, which otherwise would be considered the most desirable thing (in both the religious and materialistic worldviews).

Language describing homosexual acts tends, at least in English, to have the greatest emotional impact.

US law

It is also a legal category of speech, nominally "unprotected" under modern first amendment law. The category, however, defies neat legal classification.