Błędnie: As a group of contestants they claimed to oppose against the system. Sort of passive resistance, I would say. Poprawnie: As a group of contesters they claimed to oppose against the system. Sort of passive resistance, I would say.
"Contestant" to 'zawodnik', 'konkurent', 'rywal'. 'Kontestator' to "contester"; 'przeciwnik, oponent' to "adversary".