This is an old post but I found it so interesting that I wanted to explore it while also talking a bit about Jews, alcohol, and the outside perceptions of Jews and alcohol.

First of all- you found the same information that I did about the vegetable! But one interesting thing you might have noticed is that it mentions as basically a given that Jews were more likely to be sober (and cites a book by Charles Snyder which attempted to give an overview and explanation of the topic to that effect). This is a perception that lasted for a long time and in a lot of different places (see here for a bit of discussion on what it meant in the US during Prohibition). Were Jews actually less likely to get drunk? Very possibly, but they were definitely much less likely to get publicly drunk. (For example, according to one review Snyder says that Orthodox Jews are least likely to become alcoholics- which may or may not be true/have been true in 1954, but is complicated by the fact that alcohol and drinking are more likely to become part of more insular, religious-based services such as the holidays of Simchat Torah and Purim among the Orthodox.)

There are lots of different factors that went into this, including a push for increased respectability among (Protestant) non-Jews during the Enlightenment and beyond among modernizing Jews (which often were a reaction to accusations of alcoholism by Enlightenment era Protestant scholars). The one that is most relevant in this case, though, is a much more existential one- many Jews were innkeepers in Eastern Europe in the early modern/modern period, and a big reason for this (though not the only reason was their being known for their sobriety and not "drinking the wares."

The inns that the Jews ran were leased from local nobles and while they served all comers, the bars tended to be populated by the serfs, who were often required to frequent their noble's tavern and only their noble's tavern. Alcohol was a popular use for surplus grain from the nobles' estates, especially at times when tariffs made export a less appealing option, and within the landowning system came the raw materials, the distillery, the distributor, and the buyers, making for a very efficient system.

Jews were favored as innkeepers for a variety of reasons, including that by having Jewish-run (kosher) inns, Jewish merchants would be more likely to stop in the area- but one reason was that Jews were sober and therefore unlikely to cheat their bosses by consuming the product (not to mention the drunkenness that would come with it). This in many ways became a self-perpetuating perception, as perceived drunkenness would ruin the Jewish community's reputation in general and many of its members' livelihood in particular; this is what makes it so interesting that this phenomenon of perceived Jewish sobriety as innkeepers coincided with the rise of the chassidic movement, a spiritual revolution within Eastern European Judaism which saw alcohol as, rather than something which could hinder one's observance of the laws and connection with God, instead something that could aid and accentuate it. Alcohol achieved renewed popularity as it was drunk not just at the synagogue as part of religious rituals but at the "court" of the rebbe, or spiritual leader, as part of the chassidic spiritual connection. That said, this alcohol use tended to stay within exclusively Jewish borders rather than in the more mixed space of the tavern- Jews did not need the kind of vulnerability or reputational damage that came with public drunkenness. (This isn't to say it never happened- it was just less likely.)

All this could lead to resentment among the serfs, the patrons of the Jewish tavernkeepers. The landowners' system pre-emancipation led to the serfs being in a position in which, with little remuneration, they were harvesting the very grain which became the alcohol that they seemed compelled to buy. In the middle of it all were the Jews, who, as people outside the serf-landowner system, were able to enter as part of a middle class. While the Jews and serfs often were able to have mutually beneficial relationships, the perception of "the sober Jews who take our money to give us something that intoxicates us" still existed. This led to the kinds of conspiracy theories like the one above- if the Jews aren't drunk, it must mean that they have some secret method for remaining/becoming sober rather than having the negative effects of alcohol that we have to suffer! Of course, that was ludicrous. (Incidentally there is some discussion of whether there is a Jewish gene that ameliorates the effects of alcohol somewhat, but it's pretty marginal if it is, in fact, relevant.)