Ugly, joyless, aggressive, didactic, morose, self-righteous, unpleasant; these are just some of the words used in the press to describe the recently opened 56th Venice Biennale in Italy.

It may be the world's oldest large-scale art festival, held in priceless palazzos on Venice's many islands and attended by a group of wealthy art-world elites, but the Biennale is not beyond criticism (or protest). However, this edition — headed by veteran Nigerian curator and critic Okwui Enwezor — has seen more vitriol than many others in recent memory.

Enwezor is the Biennale's first African-born curator. His introduction into the world of large-scale exhibitions was as artistic director of the second Johannesburg Biennale in 1997, and many of the themes he addressed there can be linked to his current "All the World's Futures" exhibition in Venice. These include a fascination with cultural hybridization, border crossing and many other facets of globalization. But it's his academic and curatorial interest in what he calls "the post-colonial constellation" and an anti-capitalist bent that seems to have people frustrated. Enwezor's focus on redressing cultural and economic imbalances, and reorienting contemporary art around alternative geographies is ambitious and has led to characterizations of him as a didactic ivory-tower activist.