The question is when we should say something.

How long do we let it go? Pretend to be amused, or bemused, or too busy or too befuddled or too caught up in other things to say anything? How long do we let ourselves be intimidated out of saying anything?

Donald Trump’s campaign has been playing with the tropes of classic anti-Semitism. Yes, we understand that his son-in-law is Jewish, now his daughter is too, and so are their three children, his grandchildren. We know that Mr. Trump has not said anything specifically about Jews, as he has about Mexicans, and Syrians, and other immigrants, and women. But we are not blind and we are not deaf. What he has said — the images he has used — should signal danger to us.

“Hillary Clinton meets in secret with international banks to plot the destruction of U.S. sovereignty in order to enrich her donors,” Mr. Trump tweeted. Later, he said that the election would determine whether we are free or “in fact controlled by a small handful of global special interests rigging the system.” Those special interests, he continued, are powerful because “their financial resources are virtually unlimited, their political resources are unlimited, their media resources are unmatched.”

On first reading, it doesn’t sound all bad, does it? Who wouldn’t mind having unlimited financial resources? But it’s no joke.

In a JTA story, the writer, Ron Kampeas, compared Mr. Trump’s speech to the notorious, bilious, and deadly anti-Semitic tractate, “The Protocols of the Elders of Zion,” which its author pretended was written by Jews. The similarities are terrifying. The author rages against “radical globalization,” as Mr. Trump calls it, or “international control at political, military and economic levels,” as the Protocols author says. “The corporate media in our country is no longer involved in journalism,” Mr. Trump said. “They are a political special interest, with an agenda — and that agenda is not for you, it’s for themselves.”

The idea that the media is controlled by Jews is an old one, going back at least to the Protocols. “Through the press, we have gained the power to influence while remaining ourselves in the shade,” the Protocol’s faux-Jewish, for-real anti-Semite, wrote. “Thanks to the press we have got the gold in our hands, notwithstanding that we have had to gather it out of the oceans of blood and tears.”

This is not the first time that the Trump campaign has been accused of trafficking in anti-Semitic imagery. A few months ago, it tweeted out a picture of Hillary Clinton in a six-pointed star, imposed on piles of cash.

Jonathan Greenblatt, the executive director of the Anti-Defamation League, has called the Trump campaign out on what he sees as its willingness to play with anti-Semitic memes. In return, the campaign’s chief legal officer, Jason Greenblatt, a lawyer who lives in Teaneck, has fought back. “Jonathan Greenblatt is merely trying to divert the attention of the voters away from these facts” — the idea that “Secretary Clinton is at the heart of a global power structure that has stripped the United States of its wealth to line the pockets of corporate and political interests” — “by fabricating connections to anti-Semitism.” Jason Greenblatt continued his argument by pointing out what he calls “Mr. Trump’s lifelong commitment and support of Israel and the Jewish community.”

That well might be true. We have no idea about Mr. Trump’s commitments or support. We know it to be possible that he is using anti-Semitic tropes and memes in all innocence. He can mean them literally, without hearing the historic resonances. We have no way of knowing how they fall on his ears.

We do know, however, that those tropes and memes are dangerous. We deplore their use, and we very much hope never to hear them again.