Yes and no. Alcoholism had been thought to be a constant danger to the working man as far back as Hogarth's 18th c. series Industry and Idleness, if not further. In the US, temperance had popular support long before Prohibition. The Women's Christian Temperance Union began in 1873, and would grow to have over 300,000 members at the start of Prohibition, and there were many church denominations, like the Methodists, that supported the cause as well, and even a Prohibition Party. However, by 1900 the temperance movement also had the first use of one-issue advocacy in the US, and that was indeed by a fairly small , tightly knit organization, the Anti-Saloon League, headed by Wayne Wheeler, and this perhaps is what your teacher was referring to. Wheeler would campaign against anyone who did not toe his party line. It was not limited to shame: he had no regard for personal merit, valuable connections, political affiliations...if you did not go along with the ASL, they'd campaign for your opponent in the next election. This made them incredibly effective in gaining the legislative clout needed to get a constitutional amendment passed. And none of those against prohibition were organized at first, or had the support of churches. The Lutherans, Jews and Catholics may have been opposed, but they didn't try to unite with brewers and businessmen to create an effective opposition. So, temperance was definitely a mass-movement, with roots far back into the 19th c., but the 18th constitutional amendment that created Prohibition was made possible by the ASL.

Okrent: Last Call