President Trump is, as ever, fortunate in his enemies. Whatever one thinks of what he said in Helsinki, the overreaction is helping him plow through yet another media meltdown. Cries of “treason,” charges that the president is a Russian “asset,” and insistence that remarks at a press conference constitute impeachable offenses fire up the Democratic base. To everyone else, they seem unhinged.

What’s the fuss about, anyway? Before Helsinki, Mr. Trump had said three times—on camera—that he believed Russia meddled in the 2016 election. Yet a reporter asked him again. Why?

Mr. Trump intuits, correctly, that the media push the issue in order to undermine his legitimacy. He obviously has no interest in helping them do that, hence he challenges the question’s premise. His opponents won’t take yes for an answer because asking him over and over fuels the falsehood that he “sides with Russia over his own intelligence agencies.”

He doesn’t. But doesn’t he have good reason to be cautious about the intelligence community? There’s plenty of evidence of illicit American interference in the 2016 election, all of it to defeat Mr. Trump and elect Hillary Clinton. Yet when Mr. Trump points that out, he’s literally called a traitor—by the former head of the Central Intelligence Agency. John Brennan and James Clapper attack the president in vitriolic terms almost daily. James Comey occasionally chimes in with a Bible quote. They have a First Amendment right to do so. But constantly bashing the president casts doubt on their impartiality and professionalism while in office.

Despite all this, Mr. Trump says he believes their case that Russia meddled in 2016. So do I. But I stress the word “believe.” I don’t know and neither does anyone outside the highest levels of government. Those in the media who hyperventilate every time Mr. Trump is insufficiently emphatic in acknowledging Russian meddling don’t seem to realize he is one of the very few people in the country who’ve actually seen the underlying evidence.

Before last week’s indictments, all the intelligence community had made public was a 14-page unclassified summary that states conclusions but reveals nothing about how they were reached. That’s typical for an unclassified product, but it means the rest of us—including the media—have to take the case on faith. Yet, bizarrely, the media insist they know better than Mr. Trump.

There is more public evidence of American meddling—politicized leaks, gaming a criminal investigation, surveillance of campaign associates, and strings of biased messages by officials—than of Russian. There may be piles of secret evidence of the latter. If so, why not make more of it public? Especially since, as we have been told, acknowledging Russian interference is the patriotic imperative of our time.

From what has been made public, Russian meddling consisted of trolling social media and allegedly hacking Democratic National Committee emails. Information operations are also as old as statecraft. There’s not a lot the target country can do to stop them, beyond pointing out and ridiculing ham-fisted propaganda. Throughout the Cold War, most Americans not on the left were unaffected by far more aggressive and better-financed Soviet disinformation. But we’re supposed to believe that $10 million spent on Facebook ads and troll farms overcame Mrs. Clinton’s $768 million war chest?

Every effort should be made to protect all of America’s cybernetworks, including the privacy of campaign operatives. But it’s absurd to assume that a single vote in Michigan, Pennsylvania or Wisconsin was turned by reading John Podesta’s embarrassing emails.

Few of the president’s opponents actually say that Russia swung him the election. But that’s clearly what they insinuate and want people to believe. Mr. Trump understands this and is frustrated by it. Can you blame him?