Donald Trump's campaign to become the Republican nominee and, now, US President is one of those moments which can cause us to utterly reassess our social and political moment. It makes a mockery of the accepted wisdom on where we (or in this case the USA) are as a society, and on what we, as a nation, truly hope, fear and believe.

This is a reality TV star, with no political experience and a mixed business record, who insults vast swathes of the American electorate, and is now becoming the Republican nominee for President of the United States of America – despite being attacked by almost every high-profile member of the Republican Party.

Yes, Trump has not won the presidency or even been selected by the majority of voters in the process for the Republican candidacy. Yet, in open primaries 35-45% of voters back him. Polling in the past couple of weeks shows Clinton-Trump head-to-heads at 43:40 to Clinton. That is a huge level of support for Trump – in the UK's first-past-the-post system 35-40% would normally see a party voted into power.

Since we can no longer dismiss Trump's success as a brief or unrepresentative outlier, various new analyses are appearing. It is probably fair to say that a range of factors all played their part: increasing distrust of politicians and government; enduring changes wrought by the recent global economic downturn; the impact of globalisation on traditional industries, social cohesion and national identity; and fear caused by global terrorism.

Of all the analyses I have heard, however, the one I found most persuasive in articulating the central reason why people are not only looking for a different answer but also embracing an answer like Trump, came from the journalist Tom Slate. Speaking on the Spectator podcast recently, he said this:

"I was over in the US a couple of weeks ago covering the election for Spikd, and talking to [Trump supporters] you get a very clear sense that what is motoring them is not some sort of unreconstructed racism, it's not this sort of vitriolic bigotry - although I'm sure that plays a factor for some of them - it's the sense in which they feel that for a very long time politicians have either ignored them or smeared them when it comes particularly around issues around immigration, social issues, etcetera."

The people Slate spoke to didn't feel that politicians had simply disagreed with them. They felt that politicians had refused to listen to them and had even 'smeared' them just for having these concerns in the first place. They hadn't been told their views were wrong; they had been told their views were unspeakable. If Slate is right then, while Trump's abrasive and often insulting style gets him headlines, it is his willingness to embrace people's 'unspeakable' fears and concerns which gets him votes.

What this reveals is that debates around certain divisive topics – such as immigration – have not been won; they have been silenced. Many voters who have held strong concerns about the impact of immigration and social change have not, they feel, been allowed the space to continue to make their case and discuss solutions. They believe that the powerbrokers of public debate have simply narrowed the range of views which are permitted in society. They feel gagged. Slate suggest this has been done by both right and left; and now - almost regardless of whether they agree with Trumps policies (which are thin on the ground, and even contradictory) – these voters are hearing someone who takes their views seriously, and they are flocking to him. I would suggest that a similar analysis could apply to the rise of UKIP over the past few years.

Personally, I think many of the 'silenced' views that these Trump voters may have are misguided – which makes me all the more frustrated that they have been allowed to fester away from the glare of open and informed public debate, which alone can address these issues.

It may be too late for this US election campaign, but it is an invaluable lesson for any democracy at any time - not least us, now, as we address 'extremist' ideologies.

In the UK, the Government is increasingly embracing policy proposals which seek to shut down views which they strongly disagree with. Proposals include banning orders which may restrict an individual's ability to argue their views in public settings or perhaps on the internet, or to generally take part in public or civic life.

Now, many of the views mentioned I strongly disagree with – whether views which discriminate against women and restrict their freedoms, or anti-Semitic or anti-democratic teaching.

But this is the question: can we more effectively defeat these ideas by banning their proponents from speaking publically, or by engaging and defeating their arguments?

Stopping someone with these views from holding public meetings or being on the internet does not stop them believing what they believe, or from nurturing and spreading their ideas – even the most totalitarian regimes have struggled to do that.

These policies would certainly achieve two things, however.

First they would prevent the public debates which can defeat poisonous ideas, and which can arm those vulnerable to radicalization against such extremist views. Without airing these debates, impressionable young people (for example) will be less protected against such views.

Second, and partly as a consequence, you get what we see with Trump. You don't deal with these views; you let them fester. By telling someone who holds such a belief to be quiet, you don't persuade them they are wrong – you simply confirm to them that you are not taking their concerns and views seriously. That hardly makes people want to trust that you are right and they are wrong. All you are doing is storing up the problem for a few years down the line, when enough people start believing that view for it to burst out into public again – perhaps through a bold and charismatic leader who is not afraid to 'speak the unspeakable'.

If we really want to take on extremism, we must show why it is wrong, not push it underground.

In all the divisiveness and absurdity of Trump's rise, let's not miss the serious lesson here: shutting down a debate doesn't mean you have won, it just means you don't have the chance to tackle the beliefs you oppose – and you might not get that chance again until it's too late to defeat them.