"Bigotry seems emboldened. Our politics seems more vulnerable to conspiracy theories and outright fabrication," Bush said in a speech in New York.
He did not mention President Donald Trump by name, but Bush offered unmistakable criticism of the current administration and the controversial politics of millions of voters who swept Trump to victory last November.
"Bigotry or white supremacy in any form is blasphemy against the American creed," Bush said.
Argument "turns too easily into animosity," he added. "Disagreement escalates into dehumanization."
Unlike his Democratic successor Barack Obama, the Republican Bush has said very little publicly about Trump or the state of US politics.
Thursday's speech -- at the Bush Institute's Spirit of Liberty event -- marked a departure from that silence, an expression of concern by a former leader in a unique moment in the nation's history.
"We've seen nationalism distorted into nativism and forgotten the dynamism that immigration has always brought to America," the 71-year-old Bush said.
"We've seen our discourse degraded by casual cruelty. At times it can seem like the forces pulling us apart are stronger than the forces binding us together."
The 43rd president, observing America's "fading confidence" in free markets and international trade, lamented the "return of isolationist sentiments" in the country.
And while it is important not to ignore concerns of those whose jobs may have been lost to global economic forces, "we cannot wish globalization away," Bush said, while also stressing the importance of welcoming refugees and dissidents to US shores.
He also called for the nation to pass its civic ideals on to the next generation.
"Bullying and prejudice in our public life sets a national tone," Bush said. "The only way to pass along civic values is to first live up to them."
Bush's remarks came three days after a speech by another major Republican national figure, Senator John McCain, appeared to rebuke Trump's ideas and politics.
War hero McCain slammed what he described as "half-baked, spurious nationalism cooked up by people who would rather find scapegoats than solve problems."
