I buy into it as an option, a choice (and I don't buy into the "great artists DON'T HAVE A CHOICE!!!" idea either. Great artists might sometimes be compulsives & compulsives might sometimes be great artists, but only sometimes, and being one does not "prove" being the other) - but only one choice out of many. An overt expression of joy intended to uplift is just as valid a "purpose" as is an overt expression of alienation intended to piss people off.
I also think that there's a circular logic at work if you want to say that art must or must not be this or that, so if it is this or that, then it cannot be art. To me, that's simply creating your world in your own image and then not allowing anything else into it.
Ultimately, character of motive and quality of results don't have a whole lot to do with each other, an individual's needs and their subsequent definitions do, and people gonna be who and what they are before it's all over.
I can believe in art without a whole lot of difficulty. Much less so Artists. Like Geniuses, they exist, but in far fewer number than anybody wants to believe. But in the end...fuck it. I either like it or I don't, for whatever reason(s), and I fully reserve the full right to change my mind about any and all of it whenever and whyever.