I first came across this text fragment within a folklore tale collection which cites Schwab as a source and largely copies the text - but there were some rather curious alterations. I will mark the changes:

About the History of the Persecution of Jews in Constance [according to Schnetzler]

Around the middle of the 14th century [the people in the Lake Constance area raged against the Jews (the hated usurers) in an abominable manner, like they did in many other areas, as the superstitions of the time blamed them for all inequities of an immoral and anarchic time. In Constance] the rumor spread in Constance that a Christian was supposed to have sold holy altar bread to Jews, and a fanatical maid cried: “The body of Christ is defiled horribly by the Jews!” After this, the raging mob grabbed the next Hebrews they encountered and slaughtered them with hatchets as if they were oxen. Twelve were burned, and twelve were thrown into the Rhine. A few distinguished citizens of Constance were [noble and] brave enough to take care of the other Jews and rescue them. They were berated for having been bribed by the Jews, and the court scribe tells us that no longer had any success in life and that Heaven had punished their defense of the unrighteous with an early death.

Source: Schnetzler, A. Badisches Sagen-Buch. 1846, p. 22f.

Commentary: As we can see here, while Schwab does a decent job of providing context and condemning the attacks, Schnetzler removes the context and presents the incident more “neutrally”, which of course condemns the Jews. “It was a rumor, but it might have been true!” is the implication here. Sadly, this is not uncommon in German folklore collections, where Jews are too often portrayed badly without providing either context or condemnation of the slander. Indeed, the Brothers Grimm themselves have a track record of anti-semitism, which shines through in several of the fairy tales and legends they published.

Thus, when reading these and other tales, we should always keep in mind that the folklore collectors were not necessarily neutral observers, and had their own biases. If I spot such biases, I will call them out - but I probably won’t spot all of them.

From: Two Thousand Years of Slander - Jews in German Folklore