So would you refuse to give the only true answer to his question?

I don't understand you. The man asked how to renounce the Catholic religion. The only true answer is that this is impossible within the perspective of the Catholic religion. As a Catholic you cannot renounce the Catholic religion. Full stop. He may commit all kinds of sins, he will still be a Catholic. Except in one case: when he becomes an apostate by embracing another religion. Then he risks to be excommunicated, which from the point of view of the catholic religion is worse than death. I am just giving him the facts. God has given him the freedom of choice. This means that he is free to become an apostate, at his own risk of course.