This happened in Belgium after the initial arrests in the Dutroux case. It was called the White March and everyone wore white and carried a white balloon. It was massive, vid here https://www.youtube.com/watch?v=HyeHM448V9E Maybe we should do a similar White theme so people can connect it to Dutroux. White = purity, innocence.

The White March (French: Marche Blanche; Dutch: Witte Mars) was a demonstration in Brussels on October 20, 1996 after serial killer and criminal Marc Dutroux was arrested. The demonstrators wanted better protection for children and a better functioning justice system that could investigate the Dutroux affair independently. https://en.wikipedia.org/wiki/White_March