Via Bob Somerby, here are two ways of handling the same set of facts. The first, from the New York Times, is wrong:
Mr. Trump, the front-runner for the Republican presidential nomination, pledged a major buildup of the military, the swift destruction of the Islamic State and the rejection of trade deals that he said tied the nation’s hands. But he also pointedly rejected the nation-building of the George W. Bush administration, reminding his audience that he had opposed the Iraq war.
The second, from the Washington Post, is right:
Mr. Trump blamed previous administrations for making a mess of the Middle East — a reasonable claim, but one he littered with false assertions. He again claimed, against the known record, to have opposed the Iraq War well before it began.
Granted, the Post's version is in an editorial, where writers have more freedom to say what they want. Still, straight news reporters have, obviously, an obligation to report the news straight. And the straight truth is that Donald Trump didn't oppose the war in Iraq—not until well after it had already become a disaster, anyway. All the available evidence says so, and reporters shouldn't enable Trump's lies by repeating them unchallenged.
If Trump really opposed the war in Iraq, all he has to do is show us the evidence. It would take five minutes. He hasn't done it. He's lying.