Christian love, according to the First Epistle of John, is not mere sentiment; it is not the indiscriminate good-humor which is sometimes being mistaken for it today. It is compatible with the profoundest hatred of error, and the most zealous contending for the truth. There is nothing weak or sickly or effeminate about it. On the contrary, it requires an heroic mastery of selfishness and pride and passion.

–J. Gresham Machen, Introduction to the NT, p. 265.