The Doctrine of Separation

"The operation of an evangelical party within can only repress, and, perhaps, conceal, the evil for a time; but meanwhile, sin is committed by the compromise itself, and no permanently good result can follow. To stay in a community which fellowships all beliefs in the hope of setting matters right, is as though Abraham had stayed at Ur, or at Haran, in the hope of converting the household out of which he was called." - Spurgeon

See 2Cor. 6. This is why the Reformation failed: you cannot convert the goats, nor can you reform dead men. Justification by Faith alone, Scripture alone, God alone are all doctrinal truths in Scripture which can never be set aside nor seen as optional.

We are called OUT of and AWAY FROM that which is dead, unholy, and hostile toward God, are we not? Then why do we try to save such things as if we can dress them up to be less than what they are?

Are we called to serve vomit to the sheep?
Are we encouraged to offer poisoned water to the thirsty souls of true Christians?
Are we commanded to serve leavened bread to His Sheep?

Didn't God already speak against these things? Then why do Evangelicals believe there's another way of being justified apart from Faith? Why do they proclaim salvation apart from the preaching of the Gospel?