I've found yet another mention of six million Jews from the nauseating Jewish supremacist, communist
promoter, and gruelpropagandist Rabbi Stephen S. Wise. But first a recap of his others that I know of:
"There are 6,000,000 living, bleeding, suffering arguments in favour of Zionism."
- Speech before the Federation of American Zionists, Cooper Union, NY, June 10, 1900
"Today one-third of the Jews are on the march. Six million Jews are homeless."
- Speech before the Beth-El Congregation, Bulkeley School, Connecticut, CT, Dec 16, 1937
Wise was unsurprisingly one of the Zionists throwing about the
6,000,000 figure of HoŁocausted Jews far too early after WW2: