Wolfmueller notes that Christian joy is a rebuke to the unbelieving world. It is a provoking sting to the unbelieving conscience.
The devil argues that God is out to rob of us joy. He says: “If you do what you want, you will be happy. God’s Law stands in the way of you being happy. God’s Law is why your conscience hurts. So put away the Law. Chase your appetite, and you will be happy.” This is what is behind “gay pride.” The idea is that if enough people not only connive at but even praise my sin then my conscience won’t hurt anymore. I will finally do what I want and be happy. But such pride is anything but gay. The conscience still aches. Contentment seems farther away.
Then a Christian walks by joyful. This stings the unbeliever.