The gospel is threatened when its importance is demeaned.
How does this occur? We have stated that the gospel is the boundary of Christian fellowship. It is through your response to the gospel that determines if you are in the church and the circle of Christian fellowship or outside of it.
We have also seen that the gospel is understood within the doctrines that explain its meaning. Therefore, it is safe to say that these doctrines themselves form the boundary of Christianity. If a person denies any one of the fundamental doctrines, he denies the faith itself. Of course, if he makes no claim to be a Christian, he is simply an infidel (unbeliever).
However, if he denies one of the fundamentals of the faith while simultaneously claiming to be a Christian and expecting Christian fellowship, he is an apostate. Today, we can think of many groups that expect to be recognised as Christians, while denying one or more of the fundamental doctrines: Jehovah’s Witnesses, Mormons, Unitarians, Roman Catholics and many others. Such people demean the gospel by denying the gospel itself, while insisting that they are inside the circle of Christianity.
The Bible is very clear on how Christians are to respond to apostates.
2 John 1:9-11 Whoever transgresses and does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son. 10 If anyone comes to you and does not bring this doctrine, do not receive him into your house nor greet him; 11 for he who greets him shares in his evil deeds.
Apostates are not even to be extended civility while they are in the act of proselytizing their false gospel. By the way, this does not mean we do not show courtesy, kindness and neighbourly love to apostates as you work with them, study with them, or even live with them. It means you do not extend any recognition to them as Christians. You do not in any way act like you accept their message or endorse it. You do not do or say anything that might be construed as a concession to their apostasy.
But here comes the difficulty. It is fairly clear what to do with apostates. However, what do we do with people who profess the gospel themselves, but extend Christian recognition to apostates? What do we do with Christians who believe the fundamentals, but do not make them the boundary of Christian recognition and fellowship? J. Gresham Machen had a term for such people. He called them indifferentists. Such people show indifference towards the importance of the fundamentals, while seemingly professing it themselves.
The outstanding 20th century example of an indifferentist is Billy Graham. Graham, apart from some dubious statements made on Robert Schuller’s Hour of Power, does not seem to have publicly reneged on any of the fundamental doctrines. He would claim to believe them himself. However, since his 1957 crusade in New York, Graham has been extending Christian recognition to liberals who deny the virgin birth and deity of Christ, Roman Catholics who deny salvation by grace alone through faith alone and various other state churches (in the Communist era) that denied the gospel. His methodology of inviting all represented churches and denominations to participate in his crusades still stands, insisting upon ecumenical participation above even agreement on the fundamentals of the faith.
It is quite clear that an indifferentist demeans the gospel. He sidesteps it as the gateway of Christianity, and lowers its importance overall. He essentially tramples on it, and sets something else up as the gateway for Christian fellowship.
So what do we do with indifferentists? They demean the gospel. Indifferentism is a scandal.
The new evangelical and now mainstream evangelical answer to this question is to be indifferent towards their indifferentism, and act like nothing wrong is happening.
The fundamentalist answer has been to treat the indifferentist as a very disobedient brother, and treat him accordingly.
Thus, defined this way, a conservative Christian must be a fundamentalist in conviction. He must hate indifferentism as one of the threats to the gospel and act so as to conserve it. He will call indifferentism a scandal, rebuke the behaviour of indifferentists, and severely limit his fellowship with such disobedient men.