MOSINEE, Wis.—President Trump on Wednesday condemned political violence and called for a more civil political discourse, while also blaming the news media for “negative and false attacks.”

“No nation can succeed that tolerates violence or the threat of violence as a method of political intimidation,” Mr. Trump said at a rally in Mosinee, Wis., after a day in which law-enforcement officials found bombs mailed to prominent Democrats, including Hillary Clinton, and to CNN. He said the nation must “stop treating political opponents as being morally defective” and cease “the language of moral condemnation.”

“No one should carelessly compare political opponents to historical villains,” he added.

Mr. Trump has repeatedly called for the jailing of his opponents, particularly Mrs. Clinton—about whom his crowds at campaign rallies routinely chant, “Lock her up.” At a rally in Houston on Monday, Mr. Trump referred to the Democrats as “a mob.” Last week, he praised a Republican congressman who during his campaign body-slammed a reporter.

Mr. Trump on Wednesday made no mention of his own political rhetoric, instead jabbing at the news media, a frequent target at his campaign rallies. “The media also has a responsibility to set a civil tone and stop the endless hostility,” he said.