He once taught a generation to love science — now he’s warning America about losing its voice.

At the “No Kings” rally in Washington, D.C., Bill Nye, the beloved Science Guy, delivered a passionate speech accusing Donald Trump’s administration of silencing free speech and undermining science. “We are confronting the possible end of our republic,” Nye told the crowd. “This president and his associates cannot tolerate dissent. To them, our free speech is frightening.”

Thousands gathered as Nye, now 69, called for accountability and respect for truth. He said years of political manipulation have “undone fairness and citizens’ rights,” comparing today’s protests to the spirit of the Boston Tea Party. “We must stop the abuses of this petulant president and his circle of sycophants,” he urged.

Critics dismissed the rally as partisan, but for many, Nye’s words hit a nerve. “Science, truth, and democracy depend on brave voices,” one supporter said.

Actor @BillNye at #NoKings: “We are confronting the possible end of our republic … They must stop the abuses of this petulant president & circle of sycophants. No thrones, no crowns, no kings. This president & his associates cannot tolerate dissent. To them are free speech is… pic.twitter.com/ZEI3QwOPAS

— Tom Elliott (@tomselliott) October 18, 2025

Sometimes, the man who once explained the stars reminds us what’s worth fighting for — right here on Earth.