It started as rallies against the Gaza war in various German cities. But it became a demonstration of hardcore anti-Semitism. You could hear people scream “Hamas, Hamas. Jews in the gas.” A group attacked an Israeli couple visiting Berlin. Closer to a synagogue, others yelled “Jew, Jew, coward pig. Come out and fight for yourself.”

These incidents came as a shock to German society. But they were foreseeable, because the sentiment has been brewing for years.

So far the government has been almost blind to it. German Chancellor Angela Merkel, a Christian Democrat, is a sincere and strong friend of Israel and the Jewish people. But she needs to do more in response to these latest events. Above all, she needs to fight the anti-Semitism within German society.

Traveling in Germany and the Czech Republic last summer I witnessed several incidents. One of them broke a long friendship. I was in southern Germany to give a speech about my late husband, who, as a rabbi and author, had taught generations of non-Jewish Germans about Judaism. Years ago, I had met this particular friend through him. We were talking on her terrace when all of a sudden she commented, “You as a Christian will never get it.”

I had no clue what she was talking about. But I was hurt. I converted to Judaism more than a decade ago.

“What do you mean?” I asked. She saw my irritation and corrected herself: “I mean, you as a former Christian.” I started to guess where she was heading. My mouth got dry. “This is what they are all about,” she said. “They are always shrewd, looking only to their advantage.”

She smiled mildly. “You don’t want to see it. It’s OK.” Clearly she was implying that as a former “good” Christian, I still had notions of decency that born-Jews lacked.

Anti-Semitic notions are pervasive in German society — the upper middle class is not immune, and neither are politicians or journalists. More and more people are nurturing what researchers call “secondary anti-Semitism,” which involves accusations and assumptions that Jews are taking advantage of the Holocaust, or are obsessed with it. According to a study published by the Social Democratic Friedrich-Ebert-Foundation, 24 percent of all Germans fall into this category.

Very often people mask their anti-Semitism as criticism of Israel, which they demonize as a Nazi-like villain. According to a BBC World Poll, almost two-thirds of Germans don’t like Israel. People told my husband and me on many occasions about  “atrocities Israelis had committed,” only to end with the sigh, “They should know better, they went through it.”

It used to be taboo in postwar Germany to express anti-Semitic sentiments. That is no longer true. Complaints such as, “You are really not allowed to say anything against Jews because of the Holocaust,” which suggests Jews are to blame for a kind of self-censorship, have become common. A recent study on the new anti-Semitism calls it “a mainstream phenomenon.” One can read and hear anti-Jewish statements by ordinary citizens on almost any occasion. After the findings of Nazi-looted art in Munich, letters to newspaper editors complained about the never-ending demands of the Jews.

The government must address this kind of secondary anti-Semitism in addition to direct anti-Semitic crimes by right-wing and Islamic extremists. It will be tough for Merkel to step up and fight for something that is hard to grab. A bold and clear statement could potentially alienate her from many voters. But if she doesn’t do it, she risks doing great harm to German democracy.

Gunda Trepp of San Francisco is a German-born attorney, author and journalist who writes for several German newspapers. An audiobook, in German, based on her recorded talks with her late husband, Rabbi Leo Trepp, was published in June.