WARSAW — In conservative Poland, where even the greatest optimists have lost hope that we’ll ever have sex ed in schools, to say nothing of same-sex unions, our latest progressive leader has come from an unlikely place: professional boxing. Dariusz Michalczewski, a world-famous pugilist who goes by the nickname Tiger, recently made headlines by announcing his support for one of the country’s most prominent gay rights groups, Shoulder to Shoulder on Equality — L.G.B.T. and Friends, by appearing in a photograph with a sign reading, “I am an ally of L.G.B.T. people, because I want to live in a country where my gay friends are not discriminated against.”

Tiger, 46, is a former light heavyweight world champion who defended his title for almost 10 years. For a decade he dominated the prestigious World Boxing Organization, whose current champions include Vitali V. Klitschko and Manny Pacquiao. Now the boxer has decided to compete in the super heavyweight division — that is, the fight for minority rights in Poland.

Mr. Michalczewski is both a surprising advocate for gay rights and the perfect choice for the role: He is white, heterosexual, Catholic, rich, professionally successful and widely popular, and thus more likely to persuade conservatives than a liberal intellectual or politician. A typical young man from an economically depressed town that doesn’t have a single movie theater but has five churches might not get a chance to read a progressive manifesto. The opinions of a legendary boxer who grew up under similar circumstances, meanwhile, might prove thought-provoking.

And Mr. Michalczewski has guts: The popular sportsman did not limit himself to one photograph. He supports not only homosexuals’ right to enter into civil unions, but also their right to adopt children. In one TV appearance, he directly confronted right-wing politicians, by asking: “What if your daughter were a lesbian? What if your son were gay? If it were my child, I would love him very much. And I would support him in everything, because he’d be my child!”