It's been a funny old year, and not, in terms of public discourse, a very happy or edifying one. In the UK, Brexit turned toxic. In Hungary, Victor Orban's flag-and-faith government was accused of legalising slavery, and in Brazil, evangelical-backed Jair Bolsonaro was elected to begin his programme of cutting down rainforests. In the US, Donald Trump.

It's not only politics where the atmosphere is horrible. The mother of all religious rows, between Moscow and Constantinople over Ukraine, is escalating. There is naked hostility between various Anglican factions over sexuality, and pro- and anti-Francis Catholics are fighting like cats in a sack.

And Christian leaders raised their voices, unsurprisingly, to call for more civility, politeness and general niceness. Pope Francis appealed for peace and unity. So did the Archbishop of Canterbury and various other bishops. Not a religious leader but a person of stature, senior Republican Mitt Romney had a tilt at Trump, saying he had failed to 'elevate the national discourse with comity and mutual respect' (Trump tweeted back, 'Question will be, is he a Flake? I hope not... I won big, and he didn't.').

Well, we know what they mean. To take Brexit as a case in point, there's a nastiness about the national conversation that is at times quite startling. Everyone has an opinion, and very few of us are capable of seeing much good in the other side's. Brexiters are racist Little Englanders nostalgic for the great days of Empire. Remainers are traitorous metropolitan elitists intent on overthrowing the Will of the People. Neither of these views is generally accurate, though they are epitomised often enough to make either credible.

What the proponents of niceness fail to grasp, though, is the power of passion. And what they risk encouraging is a vapid, lowest-common-denominator politeness that fails to challenge and change deep and abiding evils.

I'm appalled by the blinkered and reactive hostility that characterises not just the Brexit debate but many others too. I'm not overly sensitive, but I always block or mute tweeters who use foul language. I can't really do that with everyone whose hatred oozes from every sentence they write; my Twitter feed would be empty. All too many of them cross the line from opposition to an idea to loathing of the person who expresses it, and that's wrong.

And yet: there is no point in trying to separate out ideas from individuality, as though the great questions of our time can be discussed as frigidly as a maths problem. Our commitments – religious and political – come from who we are. They aren't just abstractions based on calculations, they are expressions based on personality. We think we have good reasons for what we say and think, and we may well do. But we mustn't imagine that those reasons account for what we believe. If they did, we wouldn't see two people, presented with exactly the same data, arrive at completely different conclusions – and that is exactly what we do see.

In that light, appeals for niceness cut no ice. What they say is that contrary opinions don't matter – and that therefore, we ourselves don't matter. We are not important enough to be angry with, and neither are our opponents. But this is to dishonour convictions that spring not just from the mind but from the heart. They can shape the world for good or ill, and if the best lack all conviction while the worst are full of passionate intensity, we will end up with the worst.

In Christian terms, what's needed is not calmness and sweet reason, but a passionate intensity that's formed by slow and patient discipleship. There's no short cut. The process of having our secular prejudices challenged and reformed so that we pre-judge Christianly is life-long. We are always being reformed.

What Christianity has to offer to politics and politicians is, in general, character rather than policies. Discipleship is a process whereby our hearts are reshaped after the heart of Jesus – whose heart was full of compassion for the lost, and of passionate outrage at the powers of darkness that oppressed them.

There's plenty in this world to be passionate about. If I were American, I would be outraged by much of what Donald Trump says and does. As a Brit, I am outraged by Brexit. In either case, I might be wrong; but I hope my heart would be right. I would care enough to be angry, because these things matter – though I hope that in my anger I would not sin (Ephesians 4:26). But I don't want to be nice, about the crying injustices in the world today. As the poet Lucy Berry says: 'Passionless fists smash no walls./ No slaves are freed in languor./ No man-made stone is rolled back/ Except by love. And with anger.'

Follow Mark Woods on Twitter: @RevMarkWoods