Some people are thoughtless, graceless, and self-centered to the point of narcissism. If you paid them to use your free app, they would complain that you don't pay them enough. The world is full of people like that. They often vote democrat.
If he doesn't give you any followup feedback with a more apologetic attitude, tell him "Fine! Don't use the app then!" Better yet, don't dignify the attitude with an answer. Live well. That's the best revenge.