In the 1920's J. Gresham Machen knew that his denomination, The Presbyterian Church USA, was in deep trouble. It was not because they were blessing homosexuality or holding pagan ceremonies. Those things would follow later in the 20th century. During Machen's time, the PCUSA departed from the doctrine of the Bible's inerrancy. Today, rejecting the Bible's inerrancy seems to many like a non-event and is even encouraged by some.
Machen, however, saw the danger. In fact, the pressure he exerted upon the PCUSA to change course led to his being removed from the denomination. It should surprise no one that the PCUSA continues its long journey down the road of apostasy.