Obscenities considered less obscene in compounds? [NSFW]

There are at least a few cases in which a compound word or phrase, transparently containing an obscene word, seems to be considered less obscene (in some dialect/registers/circumstances) than the word itself. The two examples on which I’m fairly sure of this are:

• clusterfuck
• bullshit

Unfortunately I have no hard references beyond my own experience here: I’ve heard people use these whom I’ve never heard swear otherwise, and heard clusterfuck on the radio in programmes where I’d be amazed to hear fuck. But I recall also seing this mentioned somewhere online — a comment on Language Log, or similar — though I can’t now track that down.

So… is this phenomenon documented? well-known? quantified? And are there other notable examples?  The other potential example I can think of is motherfucker — it has I think become partially decoupled from fuck in its level of obscenity, but in the circles I know, it’s typically considered more not less obscene.

(Since I don’t have any references, I'm open to the suggestion that I’m imagining this phenomenon, over-extrapolating from a few unusual occurrences.)

Solution 1:

I strongly disagree that clusterfuck and bullshit are considered less "obscene" than fuck and shit are all by themselves. People who would be shocked by the former will be just as shocked by the latter. Even in the compounds you mention, those words still get bleeped from broadcast TV in the U.S.

Solution 2:

Contrary to Robusto's opinion, I find that certain compounds (such as those you mentioned) are indeed less offensive than the bare vulgarities you mentioned. (Others, such as "motherfucker", are worse.) However, I don't think there's any kind of broad social consensus on this, aside from highly arbitrary censorship lists used by some regulatory agencies or style guides.