The phrase "Writing about music is like dancing about architecture — it's a really stupid thing to want to do" is a catchy phrase, but it has always bothered me, particularly the "really stupid thing to want to do" part, which seems to be Elvis Costello's contribution.
The first part of the phrase that refuses to die has been around since (at least) the 1970s, and many of the people who tend to use it do not seem to be people who spend their time studying and playing the stuff that we call "classical" music.
Writing intelligently about math, science, history, literature, poetry, art, philosophy, or even architecture requires discipline-specific vocabulary. Writing about music does too. The vocabulary is not that difficult to learn, but it takes time to amass, and requires a lot of listening and a lot of observation. Writing intelligently takes work, and it usually reflects intelligent thinking. I don't think that the casual user of the phrase would consider the desire to write about the above disciplines stupid, so why should it be stupid for people to want to write about music, particularly musicians?
I am a consumer of things mathematical, scientific, historical, literary, poetic, artistic, philosophical, and architectural, but I am a producer of music. I'm proud of the music-specific vocabulary I have amassed through years of experience. I feel challenged to unravel a musical mystery and excited when I am able to articulate exactly why a particular musical passage might be strong or weak. I feel proud when I can figure out (as a performer) how to bring out compositional strengths or compensate for compositional weakness in a particular piece of music. I also find it very valuable to be able to articulate interpretive concepts to students.