Many things in this life are worth defending. We are to "fight hard for the faith" (Jude 3), defend truth (Sir 4:28), uphold the rights of the poor (Is 1:17), and make sure that the name of God is held as holy (Lk 11:2).
David was cursed viciously by a fellow Israelite as he fled Jerusalem in disgrace, having been deposed as king by his own son (2 Sm 15:14ff; 2 Sm 16:5ff). He did not defend himself or his honor. He didn't even explain that he had been wronged by his son. He accepted without bitterness the calumny of another as a chastisement which would ultimately be for his good (see Jb 2:10).
Jesus, the Son of David, took this humility a step further. "He humbled Himself" (Phil 2:8) and accepted the death of a criminal though He was innocent (Lk 23:32, 41, 47). Through it all, "He was silent and opened not His mouth" in self-defense (Is 53:7).
When we know God is our Vindicator, we can resist the temptation to defend our reputation. God intends to do a much better job of vindicating His children than we could ever do on our own behalf. Jesus announces "a day of vindication by our God" (Is 61:2). "This is the lot of the servants of the Lord, their vindication from Me, says the Lord" (Is 54:17). "He will make justice dawn for you like the light; bright as the noonday shall be your vindication" (Ps 37:6). "Your vindication shall go before you" (Is 58:8). Shout with Job: "I know that my Vindicator lives" (Jb 19:25).