Barack Obama's politics are of the naive "Equality on Earth" variety. HE never associates with any radical leftist or Islamic organizations as far as I know.
Not all communists are actual members of the Communist Party. Some wisely prefer to keep a low profile.
Chaplin was not a political figure and did not engage in political activism. His political statements come from interviews asking him about why he was being harassed. The U.S. government’s refusal to re admit him to the country in the early 1950s was embarrassing. He spent the rest of his life in England making films not agitating for political change (which he never did).