The incident comes under a conservative nationalist government that has used police and other institutions to support those loyal to its ideology. A lawmaker with the ruling party, Patryk Jaki, defended the arrest of the activist, saying "no person and no nation should be insulted. Nobody should be insulted as fascists."
But an opposition lawmaker, Slawomir Neumann, said he saw state power being used to signal to certain groups that "they can feel unpunished in Poland and will be protected by the state all the time."
"The case is absurd," Neumann said. "The case is idiotic."
The incident occurred in Przemysl, a Polish town near the border with Ukraine, during an event Saturday promoting dialogue between Poles and Ukrainians, who share a difficult history.
At one point, several Polish nationalists showed up and attempted to disrupt the event by blaring loud music. They also held up banners with the word "Wolyn 1943," a reference to a World War II-era massacre of Poles by Ukrainians.
Petro Tyma, the president of the Union of Ukrainians in Poland and a participant at Saturday's event, told The Associated Press on Monday that police were asked to react to the Polish nationalists disturbing the event but did not.
However, when the activist, Tomasz Grabowski, started chanting "Down with Polish fascism!" police arrested him, dragging him away with a European Union flag he was holding, according to footage broadcast by TVN24.
Grabowski later told the broadcaster he was held by police for six hours.
A local police spokeswoman, Marta Fac, said he was charged with insulting the Polish nation, a crime punishable by up to three years in prison.
This story has been corrected to show the day of the arrest was Saturday, not Sunday.
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