You’re probably familiar with the story of the boiled frog.

Put a frog in a pot of hot water and it jumps right out, instinctively aware of the danger to its life.

But place the frog in a pot of cold water and bring it to the boil slowly, and the frog will swim around, gradually adjusting his body temperature and acclimatising to the rising heat. By the time it realises that it is about to die, it is too late. The frog has expended all its energy and can no longer jump out of the pot.

I was reminded of this fable last week, following the revelations that Jeremy Corbyn had for a time been a member of — and even participated in — the Palestine Live Facebook group, a haven for Holocaust-deniers and antisemites. This explosive revelation was greeted by the British public with a collective shrug. Stories of Corbyn’s radicalism come so fast and furious nowadays that only a handful of political hacks seemed to care.

But it’s not the general public whose reaction concerns me. It’s the reaction of the Jewish community.

Almost unnoticed, the levels of antisemitism in politics and the public sphere which we are willing to put up with are rising, too. Once upon a time, we would have been scared witless to discover that the leader of Her Majesty’s Opposition found fit to hang out online with people who believe Jews are “demons”, that Jews are responsible for 9/11 and whose idea of a good debate is whether the term “Jew Nazi” or “Zio Nazi” is preferable.

Nowadays? The editor of the JC had to write a column admitting that he wasn’t sure the story even warranted the front page of the newspaper, so routine are its revelations.

It’s not exactly a collective shrug — most of us are quietly horrified — but the reaction was muted. We’re adjusting to the water temperature.

To be sure, there is unease in the community about the direction of travel. There is real anger, even among many Labour supporters, that the party is allowing antisemitism to flourish in the political arena. Some people express fear about what the future will bring, should Corbyn ever be elected prime minister. The vile attitude to Jews and Israel supporters on Twitter sickens and frightens those of us who still dare log on.

But daily life continues. There is no “Jew’s March” and no “Jewish lives matter” campaign. Nowadays, being abused as a Jew on social media is just a fact of life. I’m not sure how many of us even noticed the CST report that antisemitic hate crimes are at an all-time high — again.

There are even many good Jews willing to vote for Labour, in full knowledge that their leader is systematically turning a blind eye to antisemites, and is changing the tone and nature of public discourse about Jewish issues.

Compare this to the period after 7/7. My abiding memory from those years is furious discussions around every Shabbat table I frequented, about whether Jews still had a future in this country. At times, it felt like every Jew I knew was eyeing the exit, panicked by the threat of Islamic extremism and later, around the time of Operation Cast Lead, by an outpouring of anti-Israel feeling in the media. We were on emergency footing.

The irony is that the threat to Jewish life right now is far greater. Islamist terrorists are evil individuals who destroy lives, but attacks are rare and contained. Corbyn and his followers may yet one day have the instruments of state in their hands. Want to know what that might look like for us? Note what happened to Warren Morgan, the leader of Brighton and Hove council, who felt obliged to step down last month after Labour councillors criticised his highlighting of antisemitism. He’s not even Jewish.

So why have we reacted so differently? 7/7 and the Gaza War were short, sharp shocks. Like the frog, the threat was clear because it came upon us so suddenly and so violently. The antisemitism of Corbyn’s left is heating up gradually, day by day, week by week, so we adjust to every new horror and live with “the new normal”. And therein lies the danger.

We’re already half-cooked.