Dick Gregory is on a hunger strike. It will last, he wrote in 2010, until either his 80th birthday or the day his Sept. 11 conspiracy theories are validated. With the latter unlikely to happen, Mr. Gregory will have to settle for breaking the fast on his birthday next week, which he’s marking with a set at Riot Act Comedy Theater. (His actual birthday is Oct. 12.) But Gregory’s trutherism aside—he doubts the veracity of the Warren Commission, too—Hugh Hefner pulling the stand-up and activist out of the ranks of the Chitlin’ Circuit and into the mainstream is one of American comedy’s seminal moments. Long before Richard Pryor and Chris Rock ever did, Gregory challenged white audiences as aggressively as he did black audiences. In six decades of comedy, Gregory has never met a progressive cause he didn’t like, imbuing the struggle for freedom and civil rights with some much-needed humor.

Gregory performs at 7 p.m. at Riot Act Comedy Theater, 801 E Street NW. (202) 697-4900. $25.