What is "good" music?

Social Pressure. People actually love that music but only listen to it deep inside their closets, they just bash it to be like the cool beans kids.

So hating music is just a fad.

Hating certain kinds of music is only a fad for younger people. Once you have matured enough, your senses are actually keen enough to make the decisions for yourself. Calling it social pressure would explain it in most cases, but some don't feel any social pressure whatsoever and still dislike certain music. For example, I don't like rap, unless it is comedic in nature (ICP, for example), which most people that actually like rap would say is offensive to the rap genre.