From SA Mafia Wiki
Named for an SA Mafia player, the Piuro Clause is invoked to justify a vote on a player who the voter thinks is terrible. The rationale is that the player is so deficient that they will not help the game at all even if they are town and therefore it is okay to get rid of them.
This is a terrible reason to vote someone because it is usually advocating a lynch of someone the voter does not think is scummy.
This is most commonly seen as the reason given for a jokevote.