I don't think most knowledgeable sports people who argue that gymnastics is not a sport is "dissing" gymnastics. I think it is undisputed everywhere and by everyone that gymnastics requires enormous and difficult skills as well as raw physical ability. And I don't think you'll have any arguments from anyone about gymnasts being athletes. The problem I think is what people define or think a sport is. For most, they feel sports have two major components: 1) athleticism, and 2) a clear winner.
Gymnastics lacks the second component. Games like poker and chess satisfy the second condition, but not the first. They aren't sports because they don't require anything athletic. Activities like gymnastics and synchronized swimming satisfy the first condition, but not the second. They're athletic, but competition is totally "artificial". You take something beautiful and try to quantify or rank it. It's like judging yoga, or grading painters. How do you give Van Gogh a 9.6 and Monet a 9.4?
The primary virtue of gymnastics is aesthetic, and the competitive aspect they say is problematic. They are not denying it is a demanding physical activity that requires an enormous amount of talent and practice. But a sport to them is like football, baseball, basketball, hockey, and soccer, anyone watching knows who won. Races — sprints, marathons, you name it — have a clear winner. If you need judges from seven countries to vote on who won, then they feel it is not a sport.
In sports like basketball and soccer, whoever scores the most points wins. In races, whoever finishes first wins, and with the aid of modern technology, that too is clear. The Summer Olympics feature events like weight-lifting and pole vaulting. Whoever lifts the most weight or vaults the highest wins such competitions.
All sports to them has a clear winner. It is that aspect that they find problematic not that they are discounting gymnasts are not athletes.
