It's all just fucking noise
My biases
I listen to a wide variety of music. I know people with wider tastes than I, but the majority of people I know closely have comparitively narrow tastes. I have a reasonably detailed knowledge of music theory and have experience with a few instruments.
Others' biases
Despite these facts, I (and others) find themselves frequently defending their musical tastes, their knowledge of music theory and even their general intelligence. These things are brought into question by friends, family and other general consumers. There have even been concerted efforts to tell us what is music and what isn't.
One of the key areas where disagreement between parties occurs, and possibly the most-often used defence employed by either side, is the definition of terms like "music" and "noise". Even many dictionaries seem to have conflicting views. Comparing the words of both Masami Akita and Siegmund Levarie (respectively) gives a reasonable account of the rift between definitions of the terms "music" and "noise".
Visual art
Visual artists have suffered similar persecution. Place a piece of post-modern work in front of many so-called "average" citizens and the response is frequently along the lines of "my three-year-old daughter could paint better than that".
From this, it may be possible to categorise all visual art into two categories. There is that which is designed to add a little colour to a room or to look nice and there is that that tells some kind of story. The former will often be mass-produced, whereas the latter is generally a one-off work. I am certain that there would be some overlap between the two and where the line is drawn will depend on whose eyes we view through.
Parallels with music
Music may also be separated into these two broad categories. There is music that is provided (and often mass-produced from a known working template) to brighten up a room and there is that which tell a story. Even music without lyrics may fall into the latter category.
Just because a particular piece might fall into one of these two categories, and which music falls into which category depends on the listener at hand, doesn't make it any less or any more music than another piece. My preference is to generally avoid stuff that sounds (to me) like it's being created purely to be sold to the masses, but I'm not lobbying its removal from the shelves of CD retailers. I also don't ask people to turn it off because I find it both intrusive and offensive.
Suggested answers to common complaints
It'd be music without the "Cookie Monster" vocals
This is a common complaint about many forms of Metal, especially including Death and Black Metal. Those with a musical ear should notice that many of these bands (take Cradle of Filth, Anorexia Nervosa and Emperor as examples) use the vocal part more as a percussion instrument than a melodic instrument, as is the tradition. Does this mean that use of percussion makes a piece noise?
These songs are often about darker topics. An aurally pleasing voice would not have anywhere near the same impact. Try to imagine the loss of impact that would be suffered by the movie Silence Of The Lambs if Hannibal Lecter had the same voice as one of the Olsen twins.
Songs about genocide, war and the darker side of religion aren't very nice
Very true. They aren't nice. The words of George Santayana offer one reason why these topics should be discussed. He said:
Just because a group sings about a particular topic doesn't necessarily mean that they are advocating it. I also don't believe that the politics of the lyricist determines whether something is music.
It's just noise -- it doesn't follow the "rules" of music
The only reason we have the broad set of musical rules we have today is because people have stepped outside what was then the tradition. Musicians from Johann Sebastian Bach and Sergei Vasilievich Rachmaninoff to Elvis Presley and Jimi Hendrix all stepped outside the norm to create something unique.
In fact, many of the musicians who are accused of making noise as opposed to music often possess and utilise a much more detailed understanding of music theory than many of the artists often cited as being "real musicians".
Anyone can use distortion and other effects and rubbish bins and sine waves aren't real instruments
You're right. Anyone can use distortion (or delay or phasers or flangers or wah effects). Anyone could probably also use a piano. Both take a great deal of skill and practice to master and control.
As for rubbish bins? Compare a bin with a church bell or a timpani. Each are fairly crude devices that are struck to make a sound at the pertinent part of a piece of music. Just because a rubbish bin also has another use, doesn't necessarily invalidate it as a musical instrument does it?
I don't like it
Fine. That doesn't mean that the rest of us aren't allowed to. It also shouldn't have any global bearing on what we all consider music and what we consider noise.
There's plenty of music I personally dislike, despise and even hate. I'll avoid listening to it, but I don't intend to tell its listeners that they can't call it music or that they have something wrong with them.