On Thursday night, William Donohue, the president of the Catholic League, held a news conference outside an art gallery in Midtown Manhattan to denounce one of the works of art on display there: a 1987 photograph of a crucifix immersed in a jar of urine. But, when Mr. Donohue tried to enter the exhibition, the gallery would not allow him in, he said in a blog post on Friday.

“No one else was barred from entering the gallery,” he wrote. “Just me.”

The amber-hued photograph, “Immersion (Piss Christ),” has inflamed passions since the New York artist Andres Serrano first displayed it in 1989. Last year, four Christian protesters attacked the photograph with a hammer when it was on display in Avignon, France. It was also vandalized in 1997 while on display in Victoria, Australia.

All of which is ironic, Mr. Serrano said in an interview on Friday. For him, he said, the work is about his personal love of Jesus, and Jesus’s bodily torment on the cross, during which, Mr. Serrano believes, not only blood, but all Jesus’s bodily fluids, including urine, spilled out.

“The thing that offends me is that they characterize me as being an anti-Christian bigot,” he said, “and that’s far from the truth. They are barking up the wrong tree when they are saying I am not a Christian.”