Democracies are inevitably raucous, but they are often more fragile than their citizens believe. Americans, and especially President Barack Obama and the presidential candidates, should take that lesson to heart amid the recent protests and outbursts of violence.

With his unrestrained rhetoric about Mexicans, Muslims and even his fellow Republicans, Donald Trump has become a polarizing political figure of the kind the U.S. hasn't seen in many years.

His rallies are now being systematically targeted by the organized left, as MoveOn.org has admitted. Like the university left these days, progressive activists have no tolerance for dissent and want to shut down conservative speech. The provocateurs who infiltrated the Chicago venue for Trump's rally recently claimed victory when Trump prudently decided to cancel rather than risk an even uglier confrontation.

Some of these activists want to be arrested and some are not above violence. The man who bull-rushed the stage at Trump's event may have intended to do genuine harm. It's worth recalling that Black Lives Matter activists also shut down one of Sen. Bernie Sanders' events last year. Hillary Clinton and President Obama would have more credibility criticizing Trump if they also condemned the anti-speech left.

What's as disturbing, however, is Trump's apparent instinct to respond to the protesters in kind. This includes his denunciations of free political speech. A few weeks ago he said he would rewrite the libel laws to sue the press to muzzle his critics. In Kansas City, Missouri, he assailed "lying thieving reporters."

Worse, his reckless language can seem to condone violence from his supporters. Last month he responded to one protester by saying that "the guards are very gentle with him. He's walking out, like, big high-fives, smiling, laughing." Then he added, to loud cheers, "I'd like to punch him in the face, I tell ya."

Like the left-wing professor at the University of Missouri who called last year for "muscle" to evict conservatives, Trump said in Kansas City he would have responded to a protester "boom, boom, boom" as he made a fist. He also said his campaign may pay the legal fees of one of his supporters who sucker punched a protester in the face as he was being led out of a rally.

Trump has shown no desire to tone any of this down, and the cost could be high if he wins the nomination. Americans want a president they can respect, not one who is a constant source of turmoil.

REPRINTED FROM THE NEW BERN SUN JOURNAL