Because he fears Donald Trump, of course. Via The Hill:
Sen. Joe Manchin (D-W.Va.) lashed out at flag burning on Tuesday after President-elect Donald Trump raised the issue. “It’s a First Amendment right, but you do it in front of me, I’m going to beat the hell out of you,” Manchin said, according to a Roll Call reporter. Manchin is up for reelection during the 2018 cycle in a state that Trump won by more than 40 points. His comment came after Trump floated legal consequences for those who burn the American flag, which the Supreme Court ruled is protected as free speech.
“Nobody should be allowed to burn the American flag – if they do, there must be consequences – perhaps loss of citizenship or jail,” Trump tweeted Tuesday morning. Trump did not say what inspired his tweet. The Supreme Court ruled in Texas v. Johnson in 1989 that the First Amendment allows flag burning. A spokesman for Trump doubled down later Tuesday, arguing that the practice should be outlawed. “I think most Americans would agree with me that flag burning should be illegal,” Jason Miller told CNN’s “New Day.” “It’s completely despicable.”