On Thursday night the US presidential election sparked two remarkable political speeches that in different ways illuminate our times. Donald Trump turned up the ampage on the conspiracy of a “totally corrupt political establishment” . False, unsubstantiated accusations about his sexual misdemeanours, he said, were being hurled at him by a corporate media “they” controlled. He was at his most extravagant yet.

There was “no lie that they won’t tell, to hold their prestige and power at your expense”. Crooked Hillary, who should be locked up, was at the centre of it. “The claims are preposterous, ludicrous, and defy truth, common sense and logic.” Yes, these untruths hurt. But he was going to take it and rebut the lies “at an appropriate time” for the “great movement” he represented, which was going to take America back from the elite.

For all its energy and hyperbole, it was unconvincing. It was a speech whose premise you could only buy if belonging to the same Trump bubble. It was sounding off – a raging in public that may offer the person raging some relief but does not persuade anybody not in the same bubble. If he found the accusations hurtful, so what? For anybody outside the “movement”, he has amply deserved the opprobrium.

A little later, Michelle Obama spoke. She too was energetic, passionate and partisan – but she got beyond her bubble in a way that eludes Trump. Against his litany of accusations she chose to counter his rage by couching hers within a marshalled argument. Her propositions were as value laden, certainly, as Trump’s and intended to be as lethal as anything he has said. But she framed her attack in a way no one could gainsay.

There are values, in particular the way women expect to be spoken about by men, that are foundational in a civilised society, she said. What Trump had said about women, and chosen to defend as “locker room” talk, had crossed a line. “This is not normal. This is not politics as usual. This is disgraceful. It is intolerable.”

It had hit her more than she expected, she said. In explaining why, she set out a series of feminist propositions about how the psychic wrong of being objectified as no more than a body gets under a woman’s skin even as she tries to shrug it off. But she did so in language that was measured. Trump had put attitudes that should be stone-dead back at the heart of the national conversation. Her audience was spellbound. And when she said she found it personally hurtful, exposing her vulnerability, she achieved an empathy that Trump’s same admission could never do. She was pained by the betrayal of universal values and hard-won gains; his “hurt” was because his past words were catching up with him. Different leagues.

American conservatism’s morphing from the language of rationality – presenting traditional conservative concerns about the size of government and its impact on economic incentives and morality – into a language of rage and conspiracy is one of the defining realities of our age. I profoundly disagree with conservative thinkers such as Ayn Rand, Milton Friedman, Robert Nozick and Leo Strauss, but at least they mounted reasoned arguments based on first principles.

You respect them even as you argue back. The issues are never going to be settled conclusively: it is impossible to found a society entirely on libertarian individualism; but equally to overstress the role of the public realm in securing the common good has parallel hazards. You respect your intellectual or political adversary because you know you don’t hold a monopoly on truth – and if they are any good, they feel the same way. Battle is joined, and if common ground emerges you are ready to acknowledge it .

Most politicians of left and right in advanced democracies feel similarly. Conviction and personal life stories have led to a series of decisions that have got them elected as liberals or conservatives. But if they have any self-knowledge they know that their opponents have their own integrity and want outcomes that promote human betterment and merit respect. There may even be issues on which common cause can be made.

Truth no longer matters. What counts is whether a statement feels true

The right’s collapse into rage makes these ground rules of democratic politics and political argument impossible. What is Donald Trump doing demanding that Hillary Clinton go to jail? Or conniving in his supporters wearing “Trump that bitch” T-shirts at his rallies? Or wildly insisting he is the object of an elite conspiracy that is intent on gerrymandering votes to produce the result it wants? It goes beyond wild disproportionality into fantasy and delusion. It makes the mutual respect on which democratic politics is founded impossible.

Rage is absolutist. It wants to eliminate opponents, not argue with them. It justifies the gridlock and close down of government. It refuses to look for democratic compromises. It is narcissistic and wholly self-regarding, fuelled by being part of a closed belief system. It cannot accept any evidence that challenges the view that it is surrounded by conspiracy. Truth no longer matters. What counts is whether a statement feels true.

What fuels the rage is in part the stagnation of blue-collar and lower middle-class male earnings. But a politician such as Trump did not have to debase the US’s political coinage by choosing to represent this constituency in the way that he has. His “movement” does need not to betray American values to the extent he has. The legacy of lashing out at every American institution won’t disappear even if Trump loses – it will continue to poison the well.

There are echoes of this in Britain. The hard Brexiters live in the same delusional hard right bubble as Trump, treating criticism in the same way – an elite conspiracy to obstruct the popular will. There is no rationality about the EU, just rage. The consequence is analogous to civil war in both countries – a public realm where evidence-based debate becomes ever harder. The Americans are lucky to have a Michelle Obama to remind them of a different kind of politics where anger is channelled into argument.

We need to show in both countries that rage is a political, economic and cultural dead end. Hard Brexit will do that, but it may take years for the calamity to become obvious to all. Americans have a chance to do it more quickly next month. Here is hoping they seize the opportunity.