1) Duchamp's urinal (of which I am very fond) is provoking, but it's not pretty. It's just making a statement via an object. You can call that art if you want, but there are all kinds of other ways to do it, so it would be better if we could give up calling those things art (which is unlikely to happen, oh well).
2) It's a very good point about all kinds of found objects being capable of being made pretty by being framed, or by some other means of the artist suggesting to you a good way in which to look at them. However this ought to be about beauty in order to qualify as art, and being abruptly presented with something jarring is not at all the same.
3) Art goes along with a message, and the art is one thing and the message is another, and they depend on each other somewhat.

messages expressed vertically one word at a time are very inexpressive.