Concisely, what I believe is that sport and the human form in action inspired a wide array of works of art. I suppose one could argue (as you did) that the impetus for creation already existed, and that the human form in action just happened to be the chicken that hatched out of this creative egg. But I would argue that without the Western obsession with the human form, particularly the human form at toil, visual art (at least) would be vastly different than it is now. To expand beyond this really breaks down to whether you believe in the concept of "muses," which I do.

I would never dare make a statement so bold as to say that "Every artist makes art because of sports." Obviously, as the world developed, so did art and people have come to hold a wide range of opinions on every issue. Many, as yourself, denigrate art to some kind of brute show. I would never claim that work that spawns from this opinion to not be art, which leads to my last point which is more to the nature of art.

I believe in a very widely encompassing definition of art, one of the few definitions that I have heard that I truly agree with is goes something along the lines of "Art is making the impossible look easy." I'm not going to argue the virtues of football and symphonies, I wouldn't argue the virtues of a Renaissance masterpiece against a symphony, they are different formats and ought to be considered as such. This is why I think it is fairly myopic to compare and grade the merits of such disparate things, there is potential for an inherent beauty in each that the other could not attain.

I'm not asking you to like sports, I don't really care if you agree with me about the inspiration angle (I think your comment about context is interesting, even if I don't necessarily agree with it) I just simply don't see how there is anything to pity in seeing beauty in an aspect of life.