Let me give you a short crash course on the origin of the term “fundamentalist”, and how the subversion of the word has become popularized, as you say (correctly) it has.

“In response to a wave of liberalism sweeping the denominations in the first three decades of this century, Bible-believing Christians tried to mount a spiritual defense of Christian truth. Here again the common understanding today is terribly distorted … A key strategy in the defense was the publication of twelve paperback volumes from 1910 through 1915 called The Fundamentals … At the heart of the defense was the affirmation of the “essential fundamentals of the faith” by a broad base of Christian laymen and the defense of these by leading Christian scholars. The fundamentals themselves are usually identified in terms of 5 essential truths: 1) the inspiration and inerrancy of the Bible; 2) the deity of Christ and His virgin birth; 3) the substitutionary atonement of Christ’s death; 4) the literal resurrection of Christ from the dead; 5) the literal return of Christ.

As Bible-believing Christians today we have nothing to be ashamed of concerning the early “fundamentalists” attempts to defend the truth of the gospel. Indeed, the specific doctrines which were defended as The Fundamentals are what have always been affirmed throughout the ages.”

“Dr. Machen and the other men never thought of making this an “ism”. They considered these things to be a true expression of the historic Christian faith and doctrine. They were the fundamental truths of the Christian faith – doctrine which was true to the Bible; truth which they were interested in and commited to … Soon, however, the word fundamentalist came into use. As used at first, it had nothing problematic in its use either in definition or connotation. I personally, however, preferred Machen’s term “Bible-believing Christian” because that was what the whole discussion was all about.

As time passed, however, the term fundamentalist took on a connotation for many people which had no necessary relationship to its original meaning. It came to connote a form of pietism which shut Christian interest up to only a very limited view of spirituality. In this new connotation, many things having to do with the arts, culture, education, and social involvement were considered to be “unspiritual” and not a proper area of concern for a Christian … Fundamentalism also, at times, became overly harsh and lacking in love, while properly saying that the liberal doctrine that was false to the Bible had to be met with confrontation.”

– The Great Evangelical Disaster, Francis Schaeffer, 1984

This is what Fundamentalism meant, and what it has become. When you know the background, the history, and the origin of “fundamentalists”, you know what we mean when we say it has been perverted, and distorted.