Here is an interview Franken did with Buzzflash that gives some background to this story. In June, Franken appeared on a C SPAN book panel with O'Reilly and Molly Ivens, and O'Reilly blew a gasket when Franken mentioned O'Reilly's lies about a show he was formerly on, "Inside Edition", having won journalism's prestigious Peabody award.

Al Franken Buzzflash interview

Thin skinned, those right wing nuts, ain't they?