When the US administration threatened the use of the nuclear bomb against Korea to end the war quickly, DuBois wrote an open public letter to Acheson begging him not to use it, and received letters of encouragement from Einstein and Joliot-Curie (either as a result of signing the Pledge, or else as resultant to his letter to Acheson).
At that time, however, the Peace Information Center was unsuccessful in getting most Americans to even sign a copy of the Articles to the Constitution, responding for the most part that it seemed to espouse 'communist' ideas.
DuBois was arrested as an 'unregistered foreign agent' for his opposition to use of the nuclear bomb and for his opposition not only to the use of the bomb against Korea, but against American military intervention itself, calling it a 'tragic military adventure.'
DuBois fought the charges and won, because the government had no case. He was not an agent of any foreign entity. He was, that year in fact, running for Senator from NY on the Labor Party ticket... the same ticket on which the father of the current D.A. of San Francisco, Terrence Hallinan, was running for President.
By 1946, DuBois was actively voicing his views that _all_ of the post-WWII postcolonial movements for independence should receive our active support. He was largely abandoned by most of the left in that view, yet he held fast.
He was the founder of the Pan-African movement early in the century, and in fact assisted directly in the independence movement of Ghana, together with its first president, Kwame Nkrumah (see http://www.niica.on.ca/ghana/independ.htm), which was itself emerging from under British colonial rule. Obviously, DuBois's strong admonition that people ought to be allowed to follow their own national and cultural destinies was in collision with interventionist tendencies in American policy-making...
DuBois also lost faith in established intellectual circles and advocated making connections through mass movements and mass organizing in his criticism during his Wilberforce speech of 1948 wherein he abandoned the use of a concept he once espoused, the idea of the 'talented tenth' - of the ability of a limited number of elite intellectuals being able to lead the way to civil rights and freedom.
Ironically, he is remembered after his death only as a 'race relations guy' and all of his stuff, whether on sociology (in which he was a leading social scientist, and founder of empirical sociology), his peace activities, or his narratives on the Black experience in America, are all on the _same_ shelf - "African American Studies," whether it's a book store or the library. However, Noam Chomsky's writings - on the mass media, linguistics, or international policy, are all on their appropriate shelves relating to those particular topics...
I think this country is still afraid to face the truth of DuBois' writings and speeches, despite the fact that as early as 1903 he correctly predicted in 'Souls of Black Folks' that the 'color line' would be _the_ problem of the century... and aren't we still talking about it? Not necessarily doing much, but aren't we still talking about it?
A concluding thought is that in the prelude to Battle for Peace, DuBois posits that the battle for equality in the U.S. which addresses this sickness of racism in America is in fact not just 'another problem' but the key to solving the problems of other peoples around the globe purveyed by U.S. military and economic intervention and imperialism. He worries then about all the nameless, relatively unknown Black men who are incarcerated (in 1952... just think about how concerned he'd be now), and emphasizes that justice for the tragic plight of the African Americans in this country will unravel global injustices...
Currently in the U.S. there is an active campaign to free many of these prisoners who are held because of their politics, not because of a justly deserved sentence for a crime. The most famous of these is radical journalist Mumia Abu-Jamal, who was sentenced to death 16 years ago for a murder he did not commit and for which he was indicted and sentenced without a fair and just trial. See for more info about Mumia's case, for links to his writings from Death Row about the cases of the other nameless and less famous victims of the prison system, and about the national campaign to release political prisoners, "Jericho '98".