I should have replied to your second point as well. I ran into this during the Downhere debacle last week: their stance was 'how dare we criticize the outpourings of someone's soul?'
I have to say, this is a silly comment. I am a horrible singer. Even if I am praising God joyfully, my attempts at making music are not going to be very pleasant. The fact that I'm praising God is good, but that doesn't mean I should make a CD out of it and sell it! Once a singer decides to market the 'outpourings of his/her soul' for commercial purposes, I would say they become valid targets of critcism.
I guess there is an absolute to some degree: if a creation (your table, for instance) cannot serve its purpose, it's useless. Things like music do not have this restriction, because they have no defined purpose.
If I buy music, I want it to sound good, so I don't wince when a bad chord is hit. I often want it to say something meaningful, so I'm not just listening to mindless drivel. I like catchy beats and fun tunes that make me want to sing along or (if I'm in the car) exceed the speed limit (er, was that out loud?). And if an album doesn't do that, it's not serving its purpose. This is an objective standard, of course, but it is one of many examples of how art does indeed have a purpose, and some art serves it better than others.