[ksen]

This isn't talking about Christians sinning. It is talking about there being NO difference between professing believers and the world.

You are correct that Christians do sin and will sin until they die. But that is no excuse to live like the unsaved around us. If our lives are no different than our unsaved neighbors than what possible reason would they have to investigate Christianity?

[CCWoody]

It is talking about there being NO difference between professing believers and the world.

For a great many professing believers there is no difference between them and the world. And among the majority of true believers they don't know the gospel beyond the bare minimum.