“Do all things without murmurings [grumbling] and disputings [arguing]: That ye may be blameless and harmless, the sons of God, without rebuke, in the midst of a crooked and perverse nation [generation]” (Phil. 2:14,15).
Whenever there is something that is disrupting the harmony of the local assembly, each member of that Body needs to examine himself, and ask, “Lord is it I? Am I the one who has caused this problem?” The flesh can justify anything, even grumbling to others how they would have handled things differently. This only serves to cause discord among the brethren. These types of things are normally said in the shadows of the assembly hall where the battle lines are drawn for a major confrontation. When you’re not on the frontlines fighting the good fight of the faith, it’s easy to stand in the shadows and criticize others who are defending the faith. Criticism is not one of the gifts of the Spirit, but a manifestation of the flesh!
Paul wanted those at Philippi who were living in carnality to turn from it so they could be used in a greater way by the Lord. They were to be blameless, harmless, and without rebuke, so that there would be little question who they were in the eyes of the world. You see, believers have something the world is searching for: peace, purpose and hope! Therefore, it was important that these children of God maintain a consistent testimony for Christ before a crooked and perverse generation. Essentially, the apostle is challenging the Philippians to live a godly life so as not to disgrace the name of Christ before the world.
As it has been said, “When a non-believer sees a professing Christian who is argumentative, hard to get along with, and worldly in his ambitions, conversation, and behavior, the unbeliever soon forms a poor opinion of Christianity.” source