Protesters, counter-protesters and police squared up to one another on the normally peaceful plazas outside Lincoln Centre in Manhattan on Monday. The occasion: opening night of the Metropolitan Opera's new production of John Adams's 1991 work, The Death of Klinghoffer.

The opera takes as its subject the 1985 hijacking of the cruise ship Achille Lauro by Palestinian terrorists and the subsequent murder of the wheelchair-bound Jewish-American, Leon Klinghoffer. Hence the presence of dozens of protesters in wheelchairs among those listening to former mayor Rudy Giuliani, and others, rail against a work whose "emotional context truly romanticises the terrorists".

At stake on the one hand is the right of artists to take up and scrutinise controversial subjects - as Mr Adams has done previously in Nixon in China and as Alice Goodman's libretto does in Klinghoffer. On the other hand, there is the right to protest against the decision to put on this version of this show.

Plans to provide TV and radio streams of the opera were scrapped after initial protests, but the Met insists that the opera will run as planned until November 15.