From Christianity & Liberalism by J. Gresham Machen:
Salvation, in other words, was not merely through Christ, but it was only through Christ. In that little word “only” lay all the offense. Without that word there would have been no persecutions; the cultured men of the day would probably have been willing to give Jesus a place, and an honorable place, among the saviors of mankind. Without its exclusiveness, the Christian message would have seemed perfectly inoffensive to the men of that day. So modern liberalism, placing Jesus alongside other benefactors of mankind, is perfectly inoffensive in the modern world. All men speak well of it. It is entirely inoffensive. But it is also entirely futile. The offense of the Cross is done away, but so is the glory and the power.