Somewhere along the way, Christianity has got itself entangled with a soapy, soft, non-offensive concept: 'niceness.' The movement founded by a radical so offensive he got himself killed has a bunch of followers who smile at each other with creepy insincerity; deep, warm crinkles at the corners of our eyes as we say 'God bless you' to shopkeepers in the hope that our niceness will get them to church where more nice people will be there to welcome them.

Jesus did not ask us to be nice. True, it does his reputation harm if we are needlessly rude and obnoxious. Yes, being polite oils the wheels of social interaction very effectively. And who could object to genuine friendliness? The fruits of the Spirit include kindness, gentleness, and self-control. But they do not include niceness.

The Oxford English Dictionary gives various definitions for the word 'nice': giving pleasure or satisfaction, of a person: pleasant or attractive, good-natured. While there is nothing intrinsically wrong with being nice, allowing niceness to become a defining characteristic of those who profess to be Christians is not only wrong but jeopardises our ability to live the kind of lives – communal and individual – that Christ calls us to live.

The nasty side of nice

Christians who are committed to niceness above all else are generally lovely company. I've worked hard at various times to be a nice Christian – someone who will make everyone feel good about themselves, who will repel conflict like the negative end of a magnet, who will be generally liked if not deeply known. In my twenties I had therapy for the depression that had dogged me since my early teens. Turns out I was unable to identify and deal with negative emotions and experiences, and as a result they controlled me.

Last year I took my eight-year-old daughter to see the Pixar film Inside Out. How I wished it had been made when I was a child! It tells the story of Riley, a young girl whose life is turned upside down when her parents move from Minnesota to San Francisco. As the external events play out, we watch five internal characters – Joy, Sadness, Anger, Fear and Disgust – and their roles in Riley's adjustment to her new situation. By the film's conclusion, we come to see that each one is valuable and has its place in a whole and healthy human.

Christians are not supposed to be nice all the time. We are supposed to be the real, rounded, in-process people that we are. When we apply niceness to the surface of all our interactions like a layer of fine plaster of Paris, there are several consequences.

Firstly, we are unable to have genuine, life-transforming relationships. Proverbs 27:17 says, "As iron sharpens iron, so one person sharpens another." When Paul wrote to the new Christians under his care, he loved them enough to give them brutally hard critique. He challenges the church in Corinth for their jealousy and quarrelling (1 Corinthians 3:2-3), for a complete misunderstanding of God's form of wisdom, for tolerating the kind of sexual shenanigans even pagans would balk at (5:1-11), for getting drunk on communion wine and humiliating the poor in the community by not letting them eat communion bread (11:17-34) and on and on. There is nothing nice about this letter of Paul's. But "wounds from a friend can be trusted". (Proverbs 27:6) These criticisms, heard in the right spirit, had the potential to lead to repentance, growth and maturity.

Secondly, our niceness will not draw others to faith and it may well have a repellent effect. The Christian character in The Simpsons illustrates this as well as anyone. Ned Flanders' perpetual air of niceness is as enraging as it is suspect. What will draw people to faith is an encounter with Jesus, and Jesus was a lot of things but nice wasn't one of them.

Thirdly, nice people don't change the world, and as Christians we are citizens of a Kingdom in direct conflict with the kingdom of this world. When Jesus sent his 12 closest followers out on their first mission trip, he gave them an uncompromising message to deliver and no illusions about the kind of reception they were likely to receive: arrest, flogging, persecution, death. "Do not suppose that I have come to bring peace to the earth," he told them. "I did not come to bring peace, but a sword." (Matthew 10:34) There is nothing nice about being a Christ-follower. It is dangerous, exhilarating, polarising stuff.

This, then, is the challenge – how can we lose our reputation for niceness while still being known for the love we have for one another and the world? I suppose it comes down to developing a true and profound understanding of the meaning of love as embodied by our triune God. Love is not nice, but returning to that letter of Paul's to the wayward Corinthians, it is patient, kind, humble, forgiving, hopeful, trusting, persevering, protective and truthful (1 Corinthians 13: 4-7).Let's not be nice, but let's love well.