Perhaps the most threatening content is the unknown.
Consider the video for the song "Purple Stuff" by Houston singer Big Moe (2002). The song evokes a fun carnival atmosphere celebrating lean and the htown drug culture. The characteristically purple codeine laced cough syrup is euphemistically referred to throughout as "purple stuff".
In the video version, a single line is censored (2:18):
What is this offensive line? What handful of words in the midst of a song about illegally imbibing prescription cough syrup could rise above the rest as demanding censorship?
[Play along at home! (line audible at 2:18)]
Context alone is unhelpful:
...Drank stains on my FUBU and I still feel like a star
Now Ima blow up behind the wheel cause I done woke up
Wrapped around a pol(e) (-ice ?) took a sip from my cup now
Can't slip up,
Catch a playa leanin (impala ?), (wind? one?) up in the trunk now
now hut, two, three to da four
I done slammed up the (floor? four?) wit a crushed pineapple
got it gonna let it on but I ain't sippin wit dat Moe
drinkin wit' the Barre Baby I be way too throwed
And I guess a playa had about enough...
Purple Stuff (etc.)
If the playa "wind up in the trunk", then the previous line may have some violence oriented content. One possible rendering is
My "R"s a clip up
Two possibly offensive sounds in this line are the one rendered above as "R"s, which might also be "whores", in which case something sexual may have been meant; or "clip up" if "clip" is meant in the sense of a bullet dispenser.
Unfortunately, internet sources are unhelpful here. The most common rendering of the offensive line seems to be:
Some presumably lesser sources omit the "?" leaving the unintelligible (and rhythmically inadequate): Now i can't slip up clipper.
Now, presumably, these transcriptions of the lyrics all originate from the same source, as they are nearly identical in other respects, including, for example, the mistranscription of "drinkin wit' the Barre Baby" (Barre Baby being an old nickname for Big Moe) as "drinkin at the bar baby". This error, simply the result of a lack of familiarity with the singer's previous works, seems to indicate they had no feedback from the actual rappers.
Maybe whoever censored the "Purple Stuff" video did have access to complete and accurate lyrics, discovered there some unsufferable profanity at 2:18, and removed it for our collective public safety. This seems extremely unlikely.
I find it doubtful that the artists provided the TV station with a complete lyrical transcription, OR that the TV station could easily decode said line more definitively than me and the collective internets.
Most likely, it seems to me, is that the line was censored precisely because it could not be understood. And since the censor could not understand the line, he could not discard the possibility that it was profoundly offensive and damaging to the public good.
Of course, I may be mistaken about the theme of the song. Dave Chappelle identifies a (slightly?) less insidious meaning behind "purple stuff":
And, strangely, his analysis is corroborated:
k, mega groceries . . .
However, if Big Moe's Purple Stuff was indeed intended as a song about "grape drink" (and it most certainly was not), then the possibility of a line in it actually worthy of censorship is even less than on the obvious reading.
So, we are left with this: a single, unintelligible line is censored from a song, the entire theme of which is more socially disruptive in its gleeful endorsement of illicit drug consumption than any single line could be. In order to remove this feature of the song by merely silencing isolated phrases, the song as a whole would have to be completely eviscerated and left totally unintelligible.
Much better to just let the unintelligible slide, and trust the wit of the listener clever enough to decipher it to resist whatever profane suggestion it offers.