It’s clear what Israel’s western-facilitated genocide has done to Gaza. But what has it done to us? Palestinians are the “canaries in a coalmine”, the Palestinian analyst Muhammad Shehada tells me. “We’re screaming of a major warning of what’s about to come your way. When you have a media-political class that’s relishing, delighting in the murder of our children, do you think they’re going to care about yours?”

There is a warning from our recent, terrifying past that we should heed. Colonialism, warned Martinican author Aimé Césaire, “works to decivilise the coloniser, to brutalise him in the true sense of the word, to degrade him, to awaken him to buried instincts, to covetousness, violence, race hatred, and moral relativism”. The horrors of western imperialism – with its dehumanisation and violence – were, he argued, ultimately redirected into Europe in the form of fascism. This was the imperial “boomerang”, as the German-American philosopher Hannah Arendt agreed.

What will boomerang back to the west from the killing fields of Gaza? Every genocide requires the total dehumanisation of its victims, and Palestinians are no exception. They were “human animals” and “human beasts” who would suffer “hell”, declared Israeli leaders. “It is an entire nation out there that is responsible,” said Israeli president Isaac Herzog. Other Israeli politicians called for “erasing all of Gaza from the face of the Earth”. “It is not a far stretch to say there are very few innocent Palestinian civilians,” declared Republican Congressman Brian Mast, while Fox News host Jesse Waters labelled Palestinians “savages”.

But this dehumanisation goes beyond its most violent expressions. There has been no pretence that a Palestinian life has even a fraction of the worth of an Israeli life. Look at what has been normalised. Hospitals bombed and destroyed, with more than 1,700 health workers killed. Civilians massacred while sheltering in schools. More than 2,600 starving Palestinians gunned down trying to collect food since May. Teenagers shot in different parts of the body “like a game of target practice”, as British surgeon Dr Nick Maynard testified: “One day they’d be coming in predominately with gunshot wounds to the head or the neck, another day to the chest, another day to the abdomen.” Industrialised torture against detainees, from amputations of legs caused by handcuff injuries, to Israeli soldiers reportedly taking turns to rape a man with M16 rifles.

We could go on, but these are all horrors that are among humanity’s darkest moments. That they were facilitated by western governments, and cheered on or simply tolerated by western media outlets, will have profound consequences. So will the fact that westerners who protested against this wanton barbarism were demonised, sacked, deplatformed, beaten by police officers, arrested, menaced with deportation. So too will the destruction of whatever remained of an “international order”, torpedoed to protect Israel from accountability, as was the case when international criminal court judges were sanctioned by the US after it issued arrest warrants against Israeli leaders for war crimes and crimes against humanity.

Israel’s government has shifted further to the right and has sought ties with global far-right movements, such as those in France, Sweden, Spain and Hungary, understanding that such parties are its most reliable cheerleaders. Israel’s minister of diaspora and combating antisemitism even invited Tommy Robinson on an official visit – declaring him “a courageous leader on the front line against radical Islam”.

The western far-right see Israel as a model: an ethno-state waging what they see as a righteous war against Islam. The leader of Spain’s far-right Vox party declared: “We Europeans need to see what is happening to Israel,” demanding that to protect itself, Europe must “stop massive immigration and expel illegal immigrants. We do not want a Muslim Europe.” When Israel passed a law granting the right to self-determination only to Jewish people, Dutch far-right leader Geert Wilders hailed it as “fantastic”, an “example for us all”, demanding his people “define our own nation-state, our indigenous culture, our language and flag … it will help prevent us becoming Islamic.”

Listen to Israeli scholar Shmuel Lederman when he argues that Gaza became “a laboratory for genocidal violence” – but also a testing ground for “new weapons and security technologies.” Israel, notes Australian journalist Antony Loewenstein, has long tested its inventions on Palestinians, and then exported them: spyware, facial recognition and biometric databases, drones, smart fences and AI-enabled targeting systems.

Right now, Palestinians are sifting through rubble to recover their dead, praying that the genocidal onslaught ends for good, while the aid trucks Israel blocked finally arrive. But as Donald Trump observed earlier this year: “A civilisation has been wiped out in Gaza.” In the wake of the great crimes of history, there has always been a debate about what was known at the time. Despite Israel’s campaign of lies, distortion, deflection, gaslighting, muddying of the waters: we all knew. Not all the hideous details – whitewashed as they were by most media outlets – but more than enough. Israel’s crimes were not hidden: its leaders boasted of them, and they were live-streamed for the world to see.

The price paid by Palestinians is beyond our imagination. But what price will we pay? The west has dehumanised itself, just as a far-right movement that sees Muslims and the left as enemies within is on the rise. After the US bombed Venezuelan boats allegedly smuggling drugs, the US attorney general promised “the same approach with antifa: destroy the entire organisation, from top to bottom. We’re going to take them apart.” “Antifa” – or antifascism – is a phantom, a bogeyman that can be applied to any leftwing dissidents.

Do not expect the violent dehumanisation and dystopian military technologies perfected in Gaza to remain there. Our dark history tells us otherwise. What a pity we did not heed its lessons.

Owen Jones is a Guardian columnist

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