He had plenty to say to Frank Rich the other night in a 90-minute chat at Avery Fisher Hall. On Ethel Merman: “We found out later that she could act.” On Spanish in West Side Story: “The Sharks now sound more authentic than the Jets.” On critics: “Musicals are the only art form reviewed by ignoramuses.” And the man hates South Pacific: “It’s the happiest war I’ve ever seen.” (By the way, he says Bobby in Company is definitely not gay.)