Brian McLaren, the emergent Church leader and author of A Generous Orthodoxy – a brilliant book title that's become a description of a whole theological ethos – has thrown down another gauntlet to conservative Christians by rewriting old hymns he regards as too militaristic.

One of the worst culprits, he says, is Onward Christian Soldiers, written as a Sunday School hymn by the 19th-century English clergyman Sabine Baring-Gould. McLaren told Baptist News Global he was inspired to rewrite it by the "Islamophobia, xenophobia, overt and covert racism and other ugly social realities" that are "still so strong in our heavily churched culture".

"So much about the original hymn is disturbing to me," he said. "For example, it speaks ambiguously of 'the foe' — which could (in the minds of some) refer to our neighbours outside the church. It would be very different if it identified 'the foe' as, for example, corporate greed, racism, domestic violence, apathy or pride. But the ambiguity leaves room for trouble, I think. The hymn models Christian mission on warfare 'against flesh and blood' — the very opposite of what Jesus and Paul taught."

McLaren's rewritten version begins, "Onward, all disciples, in the path of peace,/ Just as Jesus taught us, love your enemies..."

Other lines include: "We now face our failures in remorse and tears/ We must hammer plowshares from our swords and spears..." and "All regimes of violence, dominating power,/ They will boast of victory for their fragile hour..."

The chorus, instead of the original's "Onward Christian soldiers, marching as to war/With the cross of Jesus, going on before" is: "Onward, all disciples, in humility/ Walk with God, do justice, love wholeheartedly."

McLaren is not the first to express doubts about Onward Christian Soldiers, and the increasingly militaristic and aggressive tone of some sections of conservative Christians in the US has perhaps rightly sharpened anxieties. Baring-Gould himself was a most interesting character. He married a mill-girl half his age and had so many children he couldn't remember them all. He collected folklore and was an expert on werewolves, and would probably have been horrified to think his song – which was not written for publication – would ever be associated with violence.

His "Christian soldiers" were a Sunday School procession, not anti-Government survivalists or Tea Party militants, and the enemy was more likely to be failure to wash behind the ears than the onrushing hordes of Islam.

Hymns do pass out of use, and it isn't always possible to rescue them by rewriting them. But it's worth putting up a fight for the best ones, including Onward Christian Soldiers. Paul is not afraid to use military imagery (Ephesians 6:10-17), and we shouldn't be squeamish either – though we should be very, very careful how we do it. Careless talk about crusades, which are remembered very differently in the Muslim world, is not very helpful in the current climate.

But the other problem with McLaren's hymn is that, with all due respect, it's not very good. Baring-Gould's is full of concrete nouns, bright images of crowns and thrones and kingdoms, hell's foundations quivering and the Church of God like a mighty army. And it all rhymes as it ought to, and every stress falls in the right place. McLaren's is worthy, but vague. Its language is conventional, all about prejudice, regimes of violence, the "power of service" and the "adventure of the living God". And "peace" doesn't rhyme with "enemies" and the sentence "Justice, flowing free,/ Makes our deserts bloom in Eden-like beauty" really cannot end with the stress on the "ty" of "beauty".

McLaren is a wonderful theologian and an admirable activist, but I shall stick with Baring-Gould on this one.

Mark Woods is the author of Salvation Songs: 70 great hymns and their stories. Follow him on Twitter: @RevMarkWoods