I care not at all for an open enemy of the church, such as the papists with their power and persecutions; I regard them not, for by them the true church cannot receive hurt, nor can they hinder God’s Word; nay, the church, through their raging and persecution, rather increases. But it is the inward evil of false brethren that will do mischief to the church. Judas betrayed Christ; the false apostles confused and falsified the gospel. Such are the real fellows through whom the devil rages and spoils the church. — Martin Luther
Likewise, it isn’t the angry atheist who causes trouble for the Church today but the pseudo-Christian who appears to the world like a real believer but who instead believes nothing and affirms nothing and witnesses to nothing but their own fanciful imaginings. Chief among these sort are the likes of Joel Osteen and Rob Bell and Rachel Held Evans and the other false believers who besmirch the name of Christianity with their anti-Christian notions.
I prefer atheists and agnostics to pretenders to Christianity.