How does the Social Gospel relate to the Gospel of Grace; or are they mutually exclusive?

There has historically been opposition by Fundamentalists to the "Social Gospel" presented by Liberal churches in the early 20th Century, and an emphasis placed on the "Gospel of Grace" by Conservative denominations in response. Since both the Old Testament and the New Testament spoke of "social activism", and both Testaments spoke of "Faith for pleasing God", are these two Gospels simply ***two sides of the same coin***? [Zechariah 7:9-10, James 1:27] Are they both two different facets of the grand Kingdom of God? Or are they mutually incompatible? One or the other being "a different Gospel" Paul warned about in Galatians 1? If compatible, how do they relate? [And by extension, how then can liberal and conservative churches relate?] Is the word "social" as referring to social reform in the Bible, to be only redefined in modern times, as synonymous with "secular"? Can there be a Christian social reform as well?