Translation:
You will come to London. Behold, I warn you, whatever of evil or of perversity (behavior or beliefs that are considered immoral or unnatural) there is in any, whatever in all parts of the world, you will find in that city alone. Do not go to the dances of panders (people who arrange sexual relationships for others), nor mix yourself up with the herds of the stews (brothels or houses of prostitution); avoid the talus (dice games) and the dice, the theatre and the tavern. You will find more braggadocios (boastful, arrogant people) there than in all France, while the number of flatterers (people who praise excessively to gain advantage) is infinite. Stage players (actors), buffoons (clowns or jesters), those that have no hair on their bodies (eunuchs, men who have been castrated, typically to serve in positions of trust around women or in royal households), Garamantes (a North African tribe), pickthanks (flatterers or sycophants), catamites (young boys used for homosexual purposes), effeminate sodomites (men who engage in anal sex), lewd musical girls, druggists (people who manufacture or dispense drugs), lustful persons, fortunetellers, extortioners (people who obtain money through force or threats), nightly strollers (people who wander the streets at night, possibly for criminal purposes), magicians, mimics (people who imitate the speech and mannerisms of others), common beggars, tatterdemalions (raggedly dressed people)—this whole crew has filled every house. So if you do not wish to live with the shameful, you will not dwell in London.
Holy crap, I took a look at the following passages in the source linked by OP and you weren't kidding.
The text accuses the Jewish community of cannibalism during Passover, with the note apparently being a message to kill and eat the bearer. Gotta keep drumming up that religious hysteria or else people might start seeing Jews as humans.
If there’s one time you know you’re definitely not going to be cannibalized by observant Jews, it’s Passover.
Yes!
Honestly, left out the cannibalism so I didn't sound too crazy.