Latin for "it's appropriate for scandals to happen". Originally in Matthew 18:7, it's used to remind people that even if the occasional financial, political or personal scandal is undoubtably bad, a society with no scandals at all is rotten to the core.
Corruption, greed and betrayal are part of every society - the leftmost side of the bell curve that holds saints, heroes and the rest of the "common people".
If you never hear anything bad about politicians and rulers, you can be 100% sure that something dreadful happened and was covered up.
The function of the occasional scandal is to expose a problem, so that we can take steps to prevent it in the future.
The phrase must not be twisted to make it appear that scandals are good per se, or that you can adopt a laissez faire attitude towards them. The next passage in Matthew's Gospel, in fact, invokes woe on the scandal maker.
This useful trivia was brought to you by the "Stun your Opponent with Latin Phrases" corporation.