Psalm 119.39 Turn away the reproach that I dread, for your rules are good.
David prays for grace to be spared from the mockery and shame that comes from sticking to God's good laws. He is like us and obviously doesn't like to be looked down upon. He wants, as we all do, to be respected for who he is and for what he believes in. Unfortunately, he knows from bitter experience, that he is not always respected when he speaks the word of God.