THIS month alone, America’s Immigration and Customs Enforcement (ICE) unit has snatched more than two thousand children from their families. Factories, plants and farms have been raided, with workers lined up outside for document checks. Whole neighbourhoods have been left traumatised for a generation as ICE’s Robocop enforcers scour the streets in the name of America’s “zero tolerance” approach to immigration.

The American state is willingly ripping up families, communities and workplaces, largely, if not exclusively, because they have the wrong accent and skin colour. Conscientious Americans are standing up to this, protesting, occupying ICE headquarters, even modifying billboards to read “We make kids disappear – ICE”. These acts of solidarity, even the smaller ones, are vital when a community faces victimisation on this scale.

That’s one major reason why I will march, not just against Donald Trump, but for the rights of the immigrant children, workers and communities his state is targeting. I’m marching for them, and for us, because, unless we show that ripping kids from their parents is intolerable, these tactics will be coming here too.

Many people claim that protest is futile, that outrage just makes Trump stronger. However, this doesn’t fit with the facts. Protest has already forced Trump to make concessions: not good concessions, but concessions that have placed limits on his plans and forced him to retreat. Protest works. When it doesn’t, it’s because there’s too little of it, or because we’ve substituted the online echo chamber for the streets.

When the good citizens of Edinburgh hounded Nigel Farage, Trump’s man in Britain, it probably didn’t stop anyone voting Ukip. But it certainly served to remind the BBC and other “liberal” journalists that there are fee payers and voters who actively dislike his rhetoric. Previously, politicians, hemmed in by the pull of the centre ground, kept trying to meet Farage halfway. Choosing appeasement over confrontation, centrists presented their own policy as a more pragmatic way to bring immigrant numbers down. Wary BBC officials, anxious to demonstrate their authenticity by “taking immigration seriously”, actively pandered to him, and invited him to air his views at every opportunity. This combination of weak politicians and discreditable journalism normalised racism, leading to the gradual subsidence of British politics towards a Ukip agenda.

The Edinburgh protest, in my view, was the closest we came to halting this sinking process, and to strengthening the resolve of principled anti-racism, which was the only way to beat Farage. After it, opposition to Farage suddenly had a voice. He looked weak, silly and defensive. It’s just a pity it came too late. By then, Farage had already captured the agenda of British politics, and the rest is history. Protest wasn’t the trouble. The trouble was, it came too late.

People say that protest didn’t stop the invasion of Iraq. That’s true. But it’s stopped at least two invasions since. Thanks to Stop the War, Tony Blair will be remembered as a fugitive from justice, and rightly so. He’s still running around free, earning millions from dictatorships and spouting his views, but protest has guaranteed that history will remember him as a war criminal, and, for this criminally vain man, that’s a form of justice.

Protest also ensured that public opinion in Scotland, England, Wales and Ireland is inherently sceptical of foreign invasions, a break with generations of imperial attitudes.

No, it’s not enough. It doesn’t take back hundreds of thousands, perhaps millions, of unnecessary deaths. But without protest, there would be no Chilcott, and we’d probably be occupying Iran by now, with inevitably dire consequences.

Protest, ultimately, can set boundaries. It can separate normal from abnormal. And that’s crucial with Donald Trump. I have marched against American presidents before, and I’m fairly sure that I’d have marched against Hillary Clinton if she continued with her foreign policy agenda. All American presidents, in my lifetime, and in the lifetime of my parents, have violated international moral norms in the name of imperial power.

But Donald Trump isn’t normal. And if we don’t start setting boundaries now, politicians across Europe are eager to learn some nasty lessons. European politics isn’t the often-imagined liberal dreamland: every new election on the continent is weakening the traditional, tired, establishment centre-left and emboldening the tough-talking demagogues.

That’s the result of decades of appeasement, of purportedly pragmatic efforts to regain legitimacy by meeting racism halfway, a tactic that has proved serially inept and has left much of Europe riddled with thoroughly creepy parliaments. We’ve got to talk tough ourselves and understand that appeasement hasn’t gained us a single vote or shred of legitimacy.

But unity is important too. We’ve got the same economic interests as many people who vote Ukip and Trump. They’ve had their prosperity stolen from them by the billionaires and the 1%.

Bernie Sanders, the man who could have beaten Trump, shows something crucial: that you can hear the voices of the white working class without throwing away your principles on racism. What a pity the Democrats didn’t listen.

Blue collar and “flyover” America was once the heartland of the left. These good old days weren’t perfect. But protest, by poor farmers against banks, by trade unions against the robber barons, by activists against segregation, united whole communities around the values and the interests of the left. We can only rebuild that trust and that value system when we get on to the streets, link arms, make our voices heard and show that we stand for something.