Other leaders, Roth said, had "buried their heads in the sand" or even exploited populist resentments.
The 704-page "World Rights 2017" report, covering key global trends in human rights as well as local conditions in 90 countries, singled out the rhetoric of Donald Trump -- a man yet to take office as US president -- as "a vivid illustration of (the) politics of intolerance."
If such voices prevail, it said, "the world risks entering a dark era."
The report said Trump's success reflected a dangerous and growing "infatuation with strongman rule" also evident in Russia, China, Venezuela and the Philippines.
HRW executive director Kenneth Roth, in presenting the report, said Trump's rise had emboldened leaders like Hun Sen in Cambodia who see Trump's election "as a greenlight to continue his repression," while one Hungarian politician justified a crackdown by saying, "This is the era of Trump."
Roth was sharply critical of Trump's pick as secretary of state, former ExxonMobil head Rex Tillerson, saying that "this is a guy who made his career by cutting deals with dictators," and who, in a Senate hearing Wednesday, looked "for excuse after excuse" not to take a stand against documented rights abuses.
HRW, which does in-person reporting in each of the 90 countries surveyed, said Syria represented "perhaps the deadliest threat to rights standards" because of the indiscriminate attacks on civilians by Syrian and allied Russian forces. It said government-backed atrocities "could easily breed new extremist groups" even if ISIS is defeated on the battleground.
But the focus of the group's report was the danger of rising populism.
HRW said politicians like Trump were exploiting a "cauldron of discontent" over joblessness, extremist attacks and increasing ethnic and racial diversity to scapegoat refugees, immigrants and minorities. Truth was "a frequent casualty."
The report asserted that Trump's policy proposals had "a practical emptiness."
Thus, by suggesting a ban on Muslims, the report said, "he demonized the very Muslim communities whose cooperation is important for identifying tomorrow’s plots." His threatened mass deportation of migrants would uproot many who contribute productively to the economy, while doing "nothing to bring back long-lost manufacturing jobs."
The report added: "We forget at our peril the demagogues of yesteryear -- the fascists, communists and their ilk who claimed privileged insight into the majority’s interest but ended up crushing the individual."
While some politicians in Britain, France, Hungary, the Netherlands and Poland were exploiting popular discontent, "too many Western leaders offer only tepid support" for human rights, Roth said.
He did credit Chancellor Angela Merkel of Germany, Prime Minister Justin Trudeau of Canada and President Barack Obama with speaking out for rights at times.
But other leaders, Roth said, had "buried their heads in the sand" or even exploited populist resentments.
The report faulted President Francois Hollande of France, who it said had "borrowed from the National Front playbook to try to make depriving French-born dual citizens of their nationality a central part of his counterterrorism policy."
And British Prime Minister Theresa May, who came to power after the populist-fueled Brexit vote, had denounced "activist left-wing human rights lawyers" for taking legal action against British troops accused of abuses in Afghanistan and Iraq.
Roth defended the report against the suggestion by one reporter that its criticism of Trump seemed partisan.
Roth said that in a break with the past, the group was calling not only on leaders of troubled countries but on their publics to take steps.
The best antidote to ascendant populism, the report said, is public activism.
"Populists thrive in a vacuum of opposition. A strong popular reaction, using every means available... is the best defense."