God is more concerned with our attitude than with his temporal dealings with the unjust. If we want God's preceptive will to be carried out on earth as it is in heaven, we should not gloat lest we provoke God to withdrawal his justice in order that his higher priority obtains, ridding us of gloating in this instance.
1. Our greatest desire should be that God's glory be on display. In this case, his just anger, which implies his temporal retribution. Our participation in that endeavor is something other than gloating, whatever that might look like.
2. We become culpable of God's justice not being meted out on earth. (That has serious implications in the political realm when parties gloat over the moral failings of their enemies.)