Cynical news consumers often assume that journalists’ personal biases seep into every story, as if a reporter writing about calls for more gun control obviously must endorse that position because it is too hard to set aside one’s own beliefs. It’s actually not that tough, in most cases.

Workers in all kinds of fields manage to do their jobs well and do them fairly while suppressing their opinions. Lawyers vigorously defend clients they don’t like, accountants accurately keep the books for companies they can’t stand, and believe it or not, journalists report truthfully on people and policies they don’t agree with. This isn’t always the case, of course, but good professionals generally find a way to keep their opinions out of it.

There are always limits to the human ability to compartmentalize feelings, however, and Donald Trump is testing them -- perhaps deliberately. His attacks on the press have become so personal, so mean-spirited, that they have to register at some level.

When Trump mocked New York Times investigative reporter Serge Kovaleski during a rally in South Carolina last month, appearing to mimic the effects of Kovaleski’s congenital joint condition, the Times issued a strong rebuke, and other media outlets covered the incident extensively. (Trump denied that his spastic motions were intended to be an impression of Kovaleski’s disability.) It was a legitimate news story, but it also felt a bit like circling the wagons.

Trump dispensed perhaps his heaviest dose of venom on Monday in Grand Rapids, Mich., where he mused about whether he would ever kill journalists.

“Uh, let’s see,” he said at one point, his hand wavering indecisively. “Eh, no, I wouldn’t. I would never kill them. But I do hate ’em, and some of them are such lying, disgusting people. It’s true.”

Trump was being glib (I think), responding to critics who questioned how he could embrace recent praise from Russian President Vladimir Putin. Since 1992, 80 journalists have been murdered in Russia, according to the Committee to Protect Journalists, though there is no proof that Putin had a hand in the killings (as Trump himself has emphasized).

Even if we assume that Trump would never seriously entertain such a thing, his total disdain for the fourth estate — whose role in a free society is so vital that the Founding Fathers sought to protect it in the First Amendment — is troubling. It’s only natural to imagine the life of a journalist under a Trump administration and to shudder at the thought.

All of this might not matter for now, while Trump is in first place, but if he falters (he leads Sen. Ted Cruz of Texas by just four points in the latest national poll and trails him in Iowa), it will be tempting for many journalists to take at least a modicum of pleasure in his downfall -- politics aside. That's human nature.

Of course, whether or not that matters politically or journalistically is an open question. Coverage has already been very critical of Trump, and Trump has in turn thrived on a critical media declaring his lead won't last and that he has problems with the truth.

But it's also clear that a guy who has clashed with the press is now making clear he has basically no respect for it. And as with many things in the Trump campaign, that's basically unprecedented.