SYDNEY, Australia — He’s been brandished “the most dangerous man on earth,” accused of being a “public advocate of genocide” and likened to Josef Mengele, the notorious Nazi “Angel of Death.”

Yet he’s also been hailed as “one of the world’s 100 most influential people” and “among the most influential philosophers alive.”

Welcome to the contradictory world that surrounds Peter Singer, the Australia-born moral philosopher who has been a professor of bioethics at Princeton University in New Jersey since 1999. Loved and loathed, one thing cannot be refuted: Singer, 65, has provoked debate about controversial issues such as infanticide, euthanasia, eugenics and animal rights.

Earlier this month, the Jewish-born, Melbourne-raised ethicist was awarded a Companion of the Order of Australia, the nation’s highest civilian honor. The citation noted his “eminent service to philosophy and bioethics as a leader of public debate and communication of ideas in the areas of global poverty animal welfare and the human condition.”

Singer, who lost three of his grandparents in the Holocaust, also has stirred debate on key issues that affect Jews, including the Israeli-Palestinian conflict, the ritual slaughter of animals, freedom of speech and charity as a means of combating global poverty.

On the ethics of Israel’s establishment, he told JTA, “Clearly there were moral flaws in the setting up of the State of Israel without proper consultation and participation by Palestinians. But that was a long time ago now, and I think that instead of looking backwards, we should try to work out the best solution for all those living in Israel and the occupied territories.”

In 2010 he signed a petition renouncing his “right of return” to Israel because it is “a form of racist privilege that abets the colonial oppression of the Palestinians.”

The petition, issued by the far-left Independent Australian Jewish Voices, an offshoot of a British group, said that “It is not right that we may ‘return’ to a state that is not ours while Palestinians are excluded and continuously dispossessed.”

Singer says he does not subscribe entirely to the views of the dissenting Jewish group, which has been marginalized by the Australian Jewish establishment.

“I take my own stance on what I judge to be right,” he said. “I have sometimes declined to sign statements from IAJV, for example, because I thought they were too one-sided, and while rightly criticizing actions taken by the Israeli government, did not also criticize actions taken by Hamas.”

Singer has been opposing ritual slaughter, or shechitah, since the 1970s, when he wrote “Animal Liberation,” which catapulted the issue of animal rights from the sidelines to the headlines and prompted some to describe Singer as the “founding father” of the animal liberation movement.

“Even when shechitah is at its best, it is still less humane than modern slaughter properly done,” said Singer, who has been a vegetarian since 1971. “No one has a right to inflict needless suffering on another sentient being. And this is needless because no one with access to a wide range of food needs to eat meat.”

Rabbi Moshe Gutnick of the Kashrut Authority of Australia and New Zealand disagrees about the suffering to animals.

“Judaism forbids causing animals any unnecessary suffering,” he said.

Gutnick adds that experts in animal welfare, such as Colorado State University professor Temple Grandin, “have stated that shechitah, when properly performed, is as humane a method as any other due to the sharpness of the knife and the rapid loss of consciousness due to loss of blood supply to the brain.”

Singer, who promotes the freedom of speech, also has defended proponents of Holocaust revisionism such as David Irving’s “absurd” opinions.

“If there are still people crazy enough to deny that the Holocaust occurred, will they be persuaded by imprisoning people who express that view?” he asked in 2006 when Irving was jailed in Austria for Holocaust denial. “On the contrary, they will be more likely to think that people are being imprisoned for expressing views that cannot be refuted by evidence and argument alone.” 

Critics have compared some of Singer’s theories to Nazi ideology. The American anti-euthanasia advocate Wesley J. Smith labeled Singer’s 1995 book “Rethinking Life and Death” as “the ‘Mein Kampf’ of the euthanasia movement.”

Singer, hailed by Time and The New Yorker magazines as among the world’s most influential people alive, favors legal reforms that would allow people to end their lives if they are terminally ill. He also argues that the life of a baby who is seriously disabled should be actively — and humanely — terminated if the baby’s parents and the doctor make that decision. He opposes simply withholding or withdrawing life support, which he says can lead to a slow and inhumane death.

“Killing a defective infant is not morally equivalent to killing a person,” he wrote, explaining that by “person” he means an individual who can anticipate the future. “Sometimes it is not wrong at all.”

Such thinking provokes a firestorm of protest from disability rights activists, among them Diane Coleman, the founder of Not Dead Yet, a U.S.-based disability group that opposes euthanasia. Coleman has called Singer “a public advocate of genocide and the most dangerous man on earth.”

Singer says of critics who use the Nazi label about him, “It’s absurd and it makes me sad,” adding that it “devalues the atrocities that the Nazis committed.”

His latest crusade is global poverty, which he argues is morally indefensible and can be substantially alleviated, if not entirely eradicated, by charity, or tzedakah.

In his 2009 book “The Life You Can Save: Acting Now to End World Poverty,” he proposes a sliding scale commensurate with income. But rather than the biblical tithe of 10 percent, he wrote that most people in the developed world should donate 5 percent and the affluent should give much larger amounts. He says he donates about 25 percent of his income to nongovernmental organizations, mostly those “helping the poor to live a better life.”

Although his family has a Passover seder — “with a beet root instead of a lamb shank” — and he celebrates Purim with his grandchildren, and Rosh Hashanah, Singer says Jewish traditions “did not play much of a role in my life.”

He concedes, though, that his family history did play a part in the development of his theories.

“As three of my grandparents died in the Holocaust, and the fourth was fortunate to survive in Theresienstadt, that was very much present in my life,” he said. “I am sure that it had some impact on my thought — on my abhorrence of cruelty, of the naked use of power over the defenseless and, of course, of racism.”

His parents, he says, gave him the choice of whether to have a bar mitzvah celebration. He declined.

“I never believed in a god,” he said. “There may have been times when I wondered if there might be a god, but it always seemed to me wildly implausible that a god worth worshiping could allow the Holocaust to occur.”

So how does the American-based professor feel having received the equivalent of the Israel Prize or the U.S. Presidential Medal of Freedom?

“It shows you don’t have to be a conformist to be recognized by your country,” he said. “And it demonstrates the value of admitting refugees, like my parents, to Australia — either they or their children and grandchildren are contributing.”

Raimond Gaita, a fellow moral philosopher from Melbourne, for decades has shared platforms and panels with Singer, often disagreeing.

“I admire the fact he writes so simply and commits himself in public discussion without wearing a professorial hat,” Gaita said.

Gaita, the emeritus professor of moral philosophy at King’s College London, particularly recalls a speech by Singer in Germany more than 20 years ago. A protester smashed Singer’s glasses as the crowd, incensed by his support for euthanasia, chanted “Singer raus, Singer raus,” echoing the Nazi-era calls of “Juden raus, Juden raus” used to call Jews out from their hiding places.

Still, Singer is steadfastly committed to his causes.

“I guess the most important thing for me is still having people come up to me after a talk and tell me that one of my books has changed their life — they’ve become a vegetarian, started donating to effective organizations working to reduce global poverty, and so on,” he said. “They’re doing good and feeling better about their lives, too.”