An attack on the Chinese artist's installation in Miami has been condemned as an act of vandalism. Why is smashing art only acceptable if an acclaimed global artist does it?

A "protest" at a Miami art museum raises some questions about what exactly art is, now.

On Sunday, a man called Maximo Caminero has smashed an artwork by Ai Weiwei, one of the most famous artists of this century and a hero to many for his defiance of the Chinese state. Cue appalled face. But this is not such a simple story. Caminero's proclaimed motive – that the Perez Museum in Miami should be showing local, not global, art – is pretty daft (I didn't know they had Ukip in Florida), but he has accidentally punched a massive hole in the logic of contemporary art.

For the "vase" that was smashed is actually a Han dynasty urn that Ai Weiwei "appropriated" for his own art by painting on it. The Han era in China was contemporary with the Roman Empire in the west. In other words, this is a major antiquity made by a Chinese artisan roughly 2,000 years ago. But that's not why the urn is valued at $1m or why its destruction is world news.

No – it's because it was part of an installation by Ai Weiwei. It is the Ai Weiwei artwork, not the Han dynasty object, that is being mourned. Perhaps it is not really an antique at all. If it's a fake, that makes the entire installation more likable. If it's not a fake, then surely Ai Weiwei, and not Caminero, is the vandal who ruined a whole bunch of antiquities by painting them whimsical colours?

I certainly would love to believe that Ai Weiwei only uses fake Han urns. I mean, why would he actually wreck real ones?

In the exhibition Ai Weiwei: According to What?, at which the vase was smashed, an array of repainted "Han urns" are shown in front of a sequence of black-and-white photographs of the artist smashing one.

This artwork is called Dropping a Han Dynasty Urn and for me it is Ai Weiwei's most provocative gesture. I feel highly provoked. It shows the artist letting go of an elegant object made with intelligence, imagination and love more than 2,000 years ago and letting it smash to bits on the ground.

Much as I wish there were, there is no apparent doubt about the authenticity of the Han artefacts Ai Weiwei uses in his art. He bought a batch of them in the 1990s and started by painting them before creating his photographed performance Dropping a Han Dynasty Urn in 1995.

What does his attack on Han art mean? I must admit I'm confused. I want to see it as a devastating satire on the modern world's alienation from the past. Ever since the Chinese Revolution began in the early 20th century, political and economic ruptures have cut off China in particular from its ancient culture. Is Ai Weiwei parodying that? Or is he mocking western art-lovers who think all Chinese art is ancient (as they may have, back in 1995)?

Ai Weiwei certainly does capture the industrial world's disconnection from making, our loss of crafts and even of basic respect for them. But he also embodies these cynical attitudes as he smashes that lovely old vase. He seems to invite further violence to art – even his own.

For this is not the first time an Ai Weiwei appropriation of a Han urn has been smashed. In 2012, art collector Uli Sigg was filmed smashing an urn in emulation of Ai Weiwei – except the one he smashed was one of Ai Weiwei's most famous works, Coca Cola Urn. Since Uli Sigg owned it, he was free to do so.

So – smashing art is interesting if an acclaimed global artist does it, and even if an art collector does it. But the guy who walks into a museum and smashes it is a vandal.

Could it be that smashing masterpieces is never interesting? That this illegal attack on art exposes the shallowness of the high end of contemporary art, where it's cool to smash Han antiquities or doodle on Goya prints?

Ai Weiwei is courageous and eloquent but this incident and his response – for he has condemned the vandal – make me wonder about the rules of art right now. The reasons for condemning one destructive act and celebrating another don't seem clear. Suddenly, the world's most respected artist looks a bit conceptually fragile.