Anti-Semitic “jokes” became one of the most talked-about subjects on French twitter last week, forcing the company to delete the anti-Semitic material.

“#unbonjuif” (#AGoodJew) became the third most talked-about keyword on the French site on October 10, and remained popular until Twitter removed the posts. Twitter users use the “#” symbol to denote keywords or phrases. Other users can search on these phrases, making it easy to find all posts on a certain subject.

In this case, the hashtag “#unbonjuif” was used on posts with anti-Semitic jokes or pictures of Holocaust victims.

“There is a deep-rooted anti-Semitism in France, and there is a very small step between racist words and racist acts,” warned Guillaume Ayne, the director of sos Racisme.

“Twitter didn’t understand the deepness of racism and anti-Semitism in France,” said Jonathan Hayoun, president of the Union of French Jewish Students (uejf).

That so many Twitter users are anti-Semitic is disturbing. A tech-savvy Twitter user isn’t the stereotypical image of an anti-Semite.

Twitter agreed to remove the posts on October 19, after the uejf threatened legal action.

Some who helped get the topic started claimed that they were protesting for free speech. Some wrote posts with the hashtag #UnBonMusulman (#a good Muslim) and #UnBonRaciste (a good racist), but these were far lest popular.

The Jewish security watchdog reported recently that the number of anti-Semitic acts had increased 45 percent over the first eight months of 2012. They concluded that Mohamed Merah’s attacks on French Jews had inspired others to copy him.

Belgium’s local election spurred what has been described as “an unprecedented wave of manifestations of anti-Semitism” at around the same time. The president of the Committee of the Belgian Jewish Organizations said that the elections, held on October 14, “were characterized by a flood of anti-Semitic events the likes of which we have never before seen.”

In Schaarbeek, near Brussels, there was a “hate campaign under the pretext of anti-Zionism.” One pamphlet described a Jewish politician as “an active Zionist and an enemy of Islam.” Voting for his party would be “stabbing Palestinians in the back,” an e-mail about him read.

Anti-Semitism is a real and growing problem in Europe. It should be a grave warning to Israel that Europe should not be trusted as an ally.