I agree that trying to force a change in the actual music is worse than requiring the parental advisory sticker, but they are both forms of censorship.
One problem is that the interpretation of lyrics is subjective, as this FBI investigation so well illustrates. Albums that sound sufficiently pop/clean/bubblegum go without the sticker when there are clearly songs explicitly about sex/drugs/etc.
For an example, look at Third Eye Blind's self-titled, debut album. Semi-Charmed Life is clearly about meth and sex, but it is sufficiently clean sounding that it gets by without a sticker.
Meanwhile, albums that sounds a little edgier, but are actually about clean, mundane subject matter have the sticker forced upon them.
IMO, the movies and games industries have much better, more objective rating systems.