Separation can easily degenerate to the level of the superficial and the external. It is very easy when dealing with this matter to shift the focus from a Spirit-filled heart where Christ reigns supremely, to a code-keeping mentality where self is applauded regularly. As a matter of fact, I am convinced that this is what has happened over the past couple of generations within Biblical Christianity. Two generations ago there lived a group of Christians who, for the most part, fleshed out their Christian lives under the lordship of Jesus Christ and in the fullness of God's Spirit. The natural by-product of such inward integrity was outward morality, consisting of both dedication to certain practices which were pleasing to Christ and abstention from those things which were not.
Unfortunately, the next generation, the one immediately preceding ours, tended to focus on the externals of outward morality, which had characterized their parents; and seemed to overlook the essentials of inward integrity, which were the real roots of their visible life style. This glaring oversight was further complicated by the fact that their parents tended to pass on the external standards without explaining the Biblical principles. In an authoritarian era, it's not difficult to see how this could happen. The effect was the development of a classical form of legalism (conformity to an outward code as the sign of spirituality), which corrupted true spirituality by shifting the focus from the internal to the external.
Today's generation has in large part forgotten the principle of lordship, which characterized their grandparents and reacted to the practice of legalism which characterized their parents. The result has been the development of a classical form of libertinism, which buys into an unprincipled and standardless form of Christianity, and which is very much like the world, while remaining very much unlike Jesus Christ. This tragic slide, over two generations of time, from lordship (where Biblical principles were understood and external standards were implemented) to legalism (where Biblical principles were ignored and external standards were exalted) to libertinism (where Biblical principles are forgotten and external standards are despised) has produced a scandalous variety of Christianity which is incapable of either confronting the culture or restraining its evil. We shall have to guard ourselves against such degeneration in our lifetime and seek to recover the Spirit-filled, Bible-based, heart focus of our grandparents, if we ever hope to be authentic fundamentalists.
Douglas McLachlan, Reclaiming Authentic Fundamentalism, pp. 137-139 (emphasis added)