Medieval illustrated manuscript depicting same-sex love, 1220-30
From Bible Moralisée, collection of the Österreichische Nationalbibliothek, Vienna
As absurd as this accusation seems, there is a kind of reasoning behind it. The long point of the poulaine was regarded as phallic. They were mostly worn by young men, who used to stuff the toes of the shoe with wool or moss to make them harder. They would then stand on street corners and wiggle them suggestively at passerbys. It is said that if somebody wore poulaines with bells sewn to the ends of them, it indicated that the wearer was available for sexual frolics.
The idea of using fashion signifiers to advertise a sexuality considered deviant by society is a familiar one for the queer community. Other items in the Museum of London's collections have played a similar role through the ages, like a Labrys earring collected as recently as 1999.
Yet more seriously, in the eyes of the church, the great length of poulaines prevented people from being able to kneel, and therefore they prevented people from praying. Thus, they became the target of censure. Priests called them Satan's Claws.
In 1362, Pope Urban V passed an edict banning them, but it didn't really stop anybody from wearing them. England would proceed to pass sumptuary laws (laws governing dress and behaviour) which set out regulations for how long somebody's poulaines could be based on their station. Commoners were charged to wear shorter poulaines than barons and knights, who were regarded as less susceptible to the kind of “sodomitic filth” that the shoe encouraged.