I guess this is the same Roger Ebert who in another review said:
I still have my membership card in Students for a Democratic Society, signed by Tom Hayden, who handed it to me at a National Student Congress in 1963, and tucked the $1 membership fee in the pocket of his flannel shirt. SDS in those days was still the "Student Department of the League for Industrial Democracy," an old-line left-labor group headed by Norman Thomas, whose statement on the back of the card made it clear the organization was nonviolent and anti-communist. Within a few years, SDS would be captured by a far-left faction which became the Weather Underground, the most violent protest group in modern American history
(For a link to the review where this last quote is found click on the title above.)
As a side note, Ebert is battling cancer and we all hope he wins that battle.In spite of his left wing views I always read his movie reviews and find them interesting and they give me a good feel for the movie from his perspective.