Question: If one cheats us, we should see this as the ripening of our negative karma and not get upset. Beyond this, if the cheat is happy for his gain, should we also rejoice for him?
Answer: The practice of rejoicing should never be for anyone’s ill-gotten gains, as gotten through greed, hatred and delusion. Just as we should praise only the praiseworthy, we should only rejoice on what is worthy, that arose from good personal efforts, from generosity, compassion and wisdom.
If not, we might end up encouraging others’ creating more negative karma. We should instead advise the cheat to make amends, to lessen already created negative karma. Whether the person heeds this or not is another matter. We should just do our part. Reporting fairly to the authorities is alright too.