Thousands of Americans participated in that most benign of civic rituals in San Jose, California, on Thursday night: seeing a presidential candidate speak. Of course, that candidate was Donald Trump, so as these engaged citizens streamed out of the arena, they were subjected to astonishing levels of violence. An angry mob pelted eggs, tomatoes, and bottles at the spectators—as well as the police, who tried (and failed) to maintain some semblance of order. Other Trump supporters were set upon and punched. One was left with blood streaming down his face. (See representative video below.)

The mayor of San Jose, Democrat Sam Liccardo, reacted angrily to the events. Not that he was particularly upset at the violent mob that attacked innocent Americans, of course. No, his ire was directed at Mr. Trump. "At some point Donald Trump needs to take responsibility for the irresponsible behavior of his campaign," the mayor said. Apparently it was downright "irresponsible" of Trump to even set foot in California's third largest city.

The Washington Post characterized the mayor's remarks as if they were just standard partisan hackery: It noted that the mayor is a "Hillary Clinton supporter." But Liccardo's remarks were far different than, say, a cable TV flack claiming that Trump's tax policy "favors the rich." (And by the way, he employed the same logic as as a slack-jawed misogynist saying of a sexual assault victim, "hey, her skirt was so short, she was asking for it.")

Mayor Liccardo justified committing violence against people with whom he disagrees politically. That's an attack on the very foundation of our system of government and the First Amendment, and a very dangerous one.