Dear 100 Hour Board,
What's the difference between avante-garde and just plain bad?
The education of the viewer. I'm no art history buff - I've just had a couple of classes where we touched on it - but things like Schoenberg's music and Fountain are much more interesting when you understand the context. Avant-garde stuff is usually more about the message and/or process than the art and that usually requires some amount of background knowledge.
I just wanted to double-testify of the truth which Sheebs did preach above. If I hear a person say "all [insert art movement/music genre/literary style/whatever] is bad," what I take that to mean is "oh, I don't understand [insert art movement/music genre/literary style/whatever]." Take some time to learn about it, and you'll likely gain an appreciation for it. I'm not saying you'll love all of it—I'm not as much a fan of Fountain (though I do love The Treachery of Images). But I do think you stand to find some new works that you'll like.