Michael Moore, who won for ''Bowling for Columbine,'' invited his fellow documentary nominees on stage for what looked like a moment of unity. ''We like nonfiction,'' he said, then proceeded to rail against what he called a ''fictitious'' president (because of the Florida voting controversy) and a war based on ''fictitious reasons.'' His speech was greeted by some cheers and louder booing. By contrast, the next speech, by the makers of the documentary short ''Two Towers,'' was met with unanimous enthusiasm as they paid tribute to police and firefighters who died on Sept. 11. Host Steve Martin defused the situation afterward by joking, ''Right now, the Teamsters are helping Michael Moore into the trunk of his limo.''