I wish I wasn't fed this bullshit down my throat all my years when I had the chance to skate everyday. Of course it is a fucking sport. It is a very physically demanding activity and you progress by repetition. Sure, some are naturally gifted and some come into skateboarding with excellent physical abilities gained by previous activities.
For me, a nerdy kid who never played much sports and fell in love with skating, progress was slow. And much of it was down to my lack of strength and the easy going attitude of skateboarding. Ironically, we are inspired by those who excel, yet we scoff at the mention of "training". What is mastering a kickflip down to 99.9% success rate so you can do combos other than fucking training?
I wish we gave kids that want to excel props for working hard on tricks not their image. We don't need to many contests and fuck sponsorship. Let us worship those who can productively use their skateboarding time and manage to work and study at the same time. Now we are breeding generations upon generations of gifted, yet misguided kids that battle for the sponsorship dollars. 99.9% of them never make it and are robbed of a good start in adult life.
TL:DR; Yes, it's a fucking sport. If you wan't to play into the whole artsy aspect of it, you first have to know how to wield the brush aka how to use you legs for tricks.