The twentieth century ushered into the church ideas regarding an enlightened humanity that required a rethinking of missions, at least in the mind of liberal theologians. They desired a focus on social issues rather than the Gospel. J. Gresham Machen stood firm against this movement seeing it as an attack on the heart of the Gospel.
In his report “The Responsibility of the Church in Our New Age,” he writes:
When I say that a true Christian church is radically intolerant, I mean simply that the church must maintain the high exclusiveness and universality of its message. It presents the gospel of Jesus Christ. Not merely as one way of salvation, but as the only way. It cannot make common cause with other faiths. It cannot agree not to proselytize. Its appeal is universal and it admits of no exceptions. All are lost in sin. None may be saved except by the way set forth in the gospel.
Listen to this important moment in Church history presented by Stephen Nichols (it takes a few seconds to get started).