We are living in the final age of apostasy (complete desertion from the truths of the Bible).  As the Lord Jesus Christ said:  "The kingdom of heaven is like unto leaven, which a woman took, and hid in three measures of meal, till the whole was leavened."  (Matthew 13:33)  

   Churches today, including so-called fundamental churches are apostate.  The gospel message presented is not the gospel message presented in the Bible. 

   Today's so-called fundamental churches have a "form of godliness" in that they practice separation, conservative dress, play biblical music...  however the gospel message that is preached is not the gospel message of the Bible.  This makes these churches more deceptive than their more liberal counterparts because they appear more holy and are thus able to fool even the most discerning.  "Having a form of godliness, but denying the power thereof: from such turn away."  (2 Timothy 3:5)  Anyone who is a true believer attending a so-called fundamental church not preaching the Gospel message of the Bible should follow the biblical Truth that these churches actually teach (to separate from error) and should apply this teaching to himself and leave that church.
A.W. Tozer writes:  “Fundamentalism has stood aloof from the Liberal in self-conscious superiority and has on its own part fallen into error, the error of textualism, which is simply orthodoxy without the Holy Ghost.  Everywhere among Conservatives we find persons who are Bible-taught but not Spirit-taught.... It was religion that put Christ on the cross, religion without the indwelling Spirit.  It is no use to deny that Christ was crucified by persons who would today be called Fundamentalists.”  (Tozer, The Divine Conquest, p. 78, 103)

   So, we must be very careful:  "Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven. Many will say to me in that day, Lord, Lord, have we not prophesied in thy name? and in thy name have cast out devils? and in thy name done many wonderful works? And then will I profess unto them, I never knew you: depart from me, ye that work iniquity."  (Matthew 7:21-23)