"It's not a religion, it's a relationship"

It's a not-uncommon fundie line. They use it when trying to distance themselves from fundies of other faiths and/or attempting to join in the “all religions are bad” bandwagon.

Burglary isn't a crime. It's a relationship with someone else's stuff.

I've found implying that jesus has a relationship with all those little children makes some folks less willing to sing "Jesus Loves the Little Children". Not quite as high as remarking on various catholic diddies though.

It comes from them believing that other denominations other than their own (or, with the less fanatical ones, all liberal churches, as well as Catholics, Jehovah's Witnesses, Christian Unitarians, and Mormons) are corrupt because they have sources of authority outside the Bible (or even just interpret the Bible "incorrectly"). Such churches tend to hold the Gospel of John, the most mystical of the four gospels and the one containing the most references to Jesus' divinity, in high regard. They also claim that the Bible is somehow free of human corruption, and believe in using that alone.

But they still have church leaders, they still have rules, and their churches are still as much of a "religion" as any other faith. It's just all about feeling "more Christian" than all the others.