Rob Bell once wrote that "'Christian' is a great noun, but a poor adjective." For anyone like me who struggled with those terms at school, I think he was suggesting that the word makes a great badge for an individual, but a bad way of delineating a marketing segment.

Bell's words (written in Velvet Elvis) are a reaction against the Church subculture's predisposition to hand out the 'Christian' label. Sometimes this has some fairly extraordinary applications (you can buy Christian socks, Christian sweets and Christian Top Trumps), but often the word's use is more culturally entrenched. We use it as shorthand to describe things which clearly complement our worldview, or which are marketed directly as such. We've become very used these phrases. But in some cases, I think they're also deeply problematic.

Christian music

The issue here isn't that Christians make music for other Christians to listen or worship to; the problem is the definition of a band or its music as 'Christian', and by implication the definition of other music as secular. With many Christians choosing to make music outside the worship industry, and with God himself being the inspiration behind all creativity, the lines are just much too blurry for that to work. Where, for instance do you categorise U2, with three committed Christian members (and one not) who increasingly write about God, grace and heaven? Or Owl City, known both for indie pop anthems and a home-brewed cover of In Christ Alone? Or Mumford & Sons? Or Gungor? As I write this, I'm coincidentally listening to Bethel's Jenn Johnson singing David Gray's Babylon, as a worship song. Try labelling that.

Christian political party

To suggest that one political party is 'Christian' is to claim that someone has definitively cracked all the issues of biblical interpretation that have divided scholars for millennia. For every Christian Republican, utterly convinced that God would defend every American's right to bear arms, there's a Christian Democrat campaigning for gun control. Free healthcare is both God's will and an abomination, depending on who you talk to. Individual politicians can be Christians – and to practise a faith in the public spotlight is an unenviable task – but whole parties simply cannot make that claim, and we definitely shouldn't make that claim about the party we happen to personally support.

Christian movie

Two problems here. Firstly, it repeats the heretical sacred/secular divide seen in the music world, where some projects are given some sort of divine seal of approval and others by implication don't. So gospel-affirming stories like The Shawshank Redemption, around which a thousand sermons has been built, are somehow seen as godless, while anything with Kirk Cameron in it passes the test. Secondly, it just turns Christianity into a marketing segment. Films are launched specifically to 'target the growing Christian market' and end up being hackneyed and predictable stories that are driven by a need to affirm its viewers' belief system – never the blueprint for great storytelling. It's no coincidence that the vast majority of 'Christian films' are utter garbage. How do you prevent the devil from having all the best movies? Don't claim all the lame ones for Jesus.

Christian charity

One conservative evangelical organisation once published a blog post calling on its supporters to refrain from giving their money to the British charity Comic Relief, writing that "some of CR's projects are Christianly dubious". Much better to give to Christian charities, who can be trusted to spend your money more wisely, they suggested. Unfortunately, this takes us into the same murky territory as any attempt to claim Jesus' political allegiance. Is it Christian, or "Christianly dubious" to support a helpline for LGBT young people who might be contemplating suicide? Is a charity only ever 'Christian' if its main purpose is to convert its beneficiaries to Christianity? Is a charity which rescues trafficked children, but doesn't do it in the name of Christ, not extending the Kingdom of God anyway? These questions leave the label in a hopeless mess; we shouldn't use it just for convenience.

I'm not suggesting that Christians shouldn't engage with all of these things; politics, the arts and the charity sector are all full of great Christians and rightly so. Nor am I saying that it's wrong for there to be a subculture around Christianity. A thousand other faiths and interest areas all have their different subcultures.

All I'm advocating is a little restraint in our use of language. The original meaning of the word 'Christian' was Christ-like, or, some translators argue, 'little Christ'. Somehow we've turned it not only into a way of segmenting our culture, but claiming our own little pocket of territory. Doing so might somehow make us feel 'safe' or encouraged, but in fact it only alienates us from the outside world, makes Christianity seem even stranger than it actually is, and replaces the whole-life-encompassing glory of the gospel with a micro-economy of the fifth and worst application of the word: Christian consumerism.

Martin Saunders is a Contributing Editor for Christian Today and the Deputy CEO of Youthscape. You can follow him on Twitter: @martinsaunders