An evangelist for Campus Crusade wrote a piece recently claiming that evangelicalism is unpopular because it makes the basic claim that it knows the truth. It's hard to gauge the issue of popularity, though evangelicalism has already succeeded in becoming the dominant religious and political movement in this country. And it's hard to see how such folks are going "against the current" on cultural issues such as gay marriage.
I also have my doubts that relativism, in practice, is as pervasive as this piece suggests. In any case, my argument with evangelicalism is not that they make truth claims, but that they have largely undercut the possibilities by which increasing knowledge can be secured. That is it is their lack of committment to the best methods we have at gaining truth is the problem. Much of this can be seen in the continual fights over the relation of science and religion.
Southern Baptist Seminary has discontinued it's program of integrating modern psychology with Christian counseling. It's being remade into a "biblical" counseling program where students will no longer receive the training neccessary for licensing or certification by professional organizations or state agencies. The school also now denies credit to students who have received clinical pastoral education in "secular" contexts.
These moves were done in response to the SBC convention's resolutions against "man made" theories as opposed to those found in "God's word" As one former student noted, this "movement away from science reveals a lack of faith, or at least a fear that somehow science is outside the realm of God's creation and domain". That is, there is lack of trust that God can speak to us in any context outside of the church, pitting the sciences and other disciplines against faith.
And there's the continued fights over evolution versus intelligent design in the k-12 public schools. The ID movement is going after universities as well. The problem with ID is that it fails to produce a theory of origins or testable hypotheses. It's rather a place holder for the unknown. The problem, as Bonhoeffer noted, is this produces a God of the gaps which continues to shrink with increasing knowledge. It certainly does nothing to further knowledge. And without such a committment what does it mean to "follow the truth"?
When I was an undergrad in InterVarsity I was told to be fearful of the humanities and philosophy professors because you might hear theories which could shake your faith. But a world where the sciences, historical work, etc. is to be feared or shuffeled off to the corner so as to not touch religious faith became untenable to me. I wanted to live in a unified world, where knowledge from any area could be welcomed, made sense out of, integrated. It was the mainline, not evangelicalism that allowed me to do this.
In the word of William Ernest Hocking: We wish to bring our religion at least into the same universe with our science and have them speak with the same voice when they verge upon the same great questions of human destiny. And surely as any one person rides one consecutive route of experience through time, so surely must all truth that belongs to one person come to the same court and enter into the same total system of his world.