Rome, March 21 - Ex-premier Matteo Renzi on Tuesday mocked 5-Star Movement (M5S) leader Beppe Grillo after he torpedoed the winner of an online poll to become the anti-establishment group's Genoa mayoral candidate. "Grillo's system is fantastic," Renzi, who is running to be re-elected head of the ruling centre-left Democratic Party (PD) next month, said in his e-news newsletter. "Basically he says: we love democracy. We love democracy so much that if the one we like wins, that's OK, but if the one we don't like wins, the candidacy goes to someone else and the unwanted candidate is expelled". On Friday Grillo sank the candidacy of poll winner Marika Cassimatis. Those within the M5S who didn't agree with his decision "should set up their own party," Grillo said Monday.