Some people on the excesses of the Lunatic Fringe have recently associated Eugène Vintras with the Priory of Sion. Why is this happening?

Here's a reminder about Eugène Vintras and his crimes:

Vintras was accused of demonic rituals and sexual excesses that involved the Black Mass. Furthermore, the French writer, poet and journalist Jules Bois highlighted the connection between Vintras and his successor, the defrocked priest Abbé Joseph-Antoine Boullan, who continued to promote Vintras's doctrines and, according to critics, further blended them with “sex magic”.

During his conviction for fraud inside prison from 1861-1864, Joseph-Antoine Boullan wrote a confession of fourteen pieces of pink paper known as Cahier Rose. It subsequently passed into the hands of Huysmans and is now in the Vatican Library.

Quoting Robert Pincus-Witten: “We know from the confession that Boullan attributed miraculous powers to consecrated hosts mixed with human excrement, and that at the conclusion of a Black Mass of 8th December, 1860, Boullan sacrificed at the altar, the child to which Adèle Chevalier had just given birth. These crimes became known only after Boullan's death” (Robert Pincus-Witten, “Occult Symbolism In France: Joséphin Péladan and The Salons de la Rose-Croix,” pages 60-61, Garland Publishing, New York & London, 1976).

Pierre Plantard himself was not immune from illegal sexual practices, as a former French Chief of French Police found out. This data by the French Police cannot be accessed until a certain period of time has passed, because of the French Privacy Law (until at least 2056). We know this only too well.