The normalisation of racism, bigotry and misogyny: this has always been one of the principal dangers of Donald Trump. Here is a man who described Mexicans as rapists and criminals and claimed a judge was biased against him because of his “Mexican heritage”. He has bragged of grabbing women’s genitals, faces multiple accusations of harassment and assault, describes women as “pigs” and “dogs”, and once suggested imprisoning women who had abortions.

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He calls entire nations “shitholes”, called white supremacists “very fine people”, and demanded a total ban on Muslims entering the United States, eventually targeting several Muslim-majority nations. Anti-Muslim hatred in the US is soaring under his administration. He has attempted to ban trans people from serving in the US military. And yet, because he is the world’s most powerful man, we risk becoming numb to such hatred, and our capacity for shock or revulsion risks becoming worn down; while his fanatical followers revel in the vulgarity of his hatred as a way to drive back gains won by women, minorities and LGBTQ people.

Although many British people opposed Theresa May’s offer of a state visit last year – on the basis that it was conferring an honour on a racist demagogue that some presidents never receive, and none have been offered so swiftly – Trump is entitled to a working visit. And equally, those of us who abhor what he represents are entitled to exercise the right to protest. When he arrives on 13 July, the Stop Trump and Stand Up to Trump campaigns will protest together: “Together Against Trump” is the banner under which we will march.

The cynical comebacks are out in force already: isn’t your protest a futile sham, just the hysterical bleating of the snowflake army? The first objective is to stop the normalisation of Trump and his bigotry. Trump’s election was a source of jubilation for the far right, which looks to him to legitimise its brand of politics. He retweeted Britain First’s racist videos, one of which claimed to depict a migrant (he wasn’t) beating up a boy on crutches.

The protest will also be a repudiation of the politics of Trump’s ally Nigel Farage, a man who has done more than most to inject hatred deeper into our politics. The demonisation of migrants and minorities – including by the “mainstream” right – is a phenomenon sweeping the western world. It has become embedded in our political cultures. A mass protest in towns and cities across Britain will represent a profound show of force against the xenophobes and the bigots. It will be a protest not simply against Trump but Trumpism, in all its guises. We know, after all, what happens when racist scapegoating is unchallenged. Look at the Windrush scandal: a “hostile environment” for undocumented migrants ended with British citizens who have lived here for decades being denied medical treatment, being kicked out of their homes and facing deportation.

A nationwide protest will offer solidarity with those targeted by the populist right, and redouble a united effort to defend them: women, Muslims, refugees, immigrants, gay and trans people and other minorities. That will not just offer comfort to besieged and frightened communities: it will join the dots, emphasising that attacks on any are interlinked, that each struggle cannot be won in isolation, and that only a broad coalition can defeat misogyny, migrant-bashing, homophobia, transphobia and anti-Muslim hatred.

Trump is engaged in a systematic attempt to roll back rights and freedoms. Some of our own politicians would like to replicate it. He is dismantling LGBTQ health programmes as well as regulations protecting LGBTQ workers and hospital patients; promoting anti-LGBTQ judicial candidates; removing guidance that defends trans students and workers; and arguing for “religious liberty” exemptions to LGBTQ anti-discrimination laws. His administration has sought to chip away at women’s right to choose.

The ascendant Jacob Rees-Mogg faction of the Tory party brims with those who would emulate Trump if they could

Alongside his pro-rich tax policies, the ascendant Jacob Rees-Mogg faction of the Tory party brims with those who would emulate Trump if they could. A mass movement in every town and city would provide a counterweight to the wholesale importing of Trumpism.

There is military aggression, too. Donald Trump is promoting warmongers such as John Bolton, one of the architects of the Iraq calamity that claimed hundreds of thousands of lives and spawned Islamic State. The danger of war with Iran, in particular, is real: the regional destabilisation it would provoke could make Iraq look like a tea party.

The instinct of May’s morally decrepit administration will be to kowtow to Trump and his thuggish entourage. If the nation’s streets brim with those offering the moral leadership our prime minister cannot, our government will be reminded that subordinating Britain to a demagogic president rejected by most of his own country will exact a political cost.

Trumpism did not invent misogyny, bigotry and racism. One danger is that his administration shifts the goalposts, promoting a sense among other hardliners of, “Well, we’re not as bad as Trump.” We live in a society where young black men are harassed by police officers, where unemployment and poverty are higher amongst racial minorities, where women are concentrated in the lowest-paid and most insecure jobs, and where millions are harassed or assaulted by men. Trumpism gives comfort to those who are happy with this.

Trump represents an exceptional danger. And that’s why we must all march.

• Owen Jones is a Guardian columnist