There are simply two kinds of music, good music and the other kind ... the only yardstick by which the result should be judged is simply that of how it sounds. If it sounds good it's successful; if it doesn't it has failed.
- Duke Ellington
In my experience, when I run into blanket judgments about musical genres or bands or individual musicians, it usually comes down to someone repeating an opinion they heard from someone else, without really examining it first. Opinions like, "the Beetles only knew 4 chords", or, "jazz is a corruption of classic music" or, "hip-hop has no merit".
At some point, someone offers a blanket opinion that leaves an impression on us. That opinion might come from someone we respect, like a teacher or a parent or a really smart friend. Then we go around repeating it like it's based on our own knowledge. And everybody does this, or at least everyone I've met. And not just about music either. I've done it, and I'm guessing everyone here has done it.
The quoted opinions above are all examples from real life:
The one about the Beetles was told to me by a good friend of mine. After questioning why she thought that, I realized she meant to say they are overrated. But she took a shortcut right around the truth based on an acquired opinion.
The following one about Jazz is from Ben Shapiro. When claiming rap wasn't music, he explained his theory of the de-evolution of music from classical down to hip hop. He got this from his dad.
The last one, about hip-hop, is from Wynton Marsalis. He agrees with Ben that hip hop is basically not music ("It has no merit, rhythmically, musically, lyrically."). Not gonna get into why Wynton thinks this, but let's just say some people question his knowledge of musical genres besides jazz.
Which brings me back to the first quote. There are simply two kinds of music...