The statement declares, simply, that the enemy is in the camp.
And, sadly, that remains the case.
“The central problem of our age is not liberalism or modernism, nor the old Roman Catholicism or the new Roman Catholicism, nor the threat of communism, nor even the threat of rationalism and the monolithic consensus which surrounds us [nor, I would add today, postmodernism or materialistic consumerism or visceral sensualism or whatever]. All these are dangerous but not the primary threat. The real problem is this: the church of the Lord Jesus Christ, individually or corporately, tending to do the Lord’s work in the power of the flesh rather than of the Spirit. The central problem is always in the midst of the people of God, not in the circumstances surrounding them.”
Francis A. Schaeffer, No Little People (Wheaton, 2003), page 66.