From Ray Ortlund's talk at the 2011 Gospel Coalition Conference (which is well worth reading in its entireity):

The Galatian churches were unstable to begin with, because the reassuring finality of “It is finished” had been eroded away by the acids of self-justification. Insecurity, anxiety, fear and anger had entered in. How could it be otherwise? Self-justification cannot create anything but an unsatisfiable demandingness, for Christ is not its satisfying provision. No matter how well a person has been raised to be courteous, self-justification must generate finger- pointing and accusing and slandering and dividing. Whatever the outcome, no one wins.

When in any church savagery erupts, the problem is not personal, a lack of niceness. The problem is theological, a lack of gospel. But where Jesus reigns by his gospel, love reigns as “a mutual protection and kindness” (Calvin). Paul was a man of courage, forthrightness and apolitical independence. He was also a man of love, humility and warmth: “You were called to freedom, brothers. Only do not use your freedom as an opportunity for the flesh, but through love serve one another. For the whole law is fulfilled in one word: ‘You shall love your neighbor as yourself’” (Galatians 5:13-14). Strong principles and humane relationships, together simultaneously, mark a church as faithful to the gospel.