They were likely pacifists, though I don't know from what stripe. There was a small, vocal minority prior to World War II who were anti-interventionists pacifists in the United States, who wanted to keep the US out of the war.
There were interesting relationships between pacifist groups in the United States, with American communists/socialists, pro-German 'American Bund' groups, and former temperance and suffrage activists sharing a common bond in opposition to American involvement in the war.
American communists broke off from opposition to the war once Hitler broke the Molotov-Von Ribbentrob pact of non-aggression between Germany and the Soviet Union.
The Popular Front, international Communist parties in Western democracies, were all being puppeteered by Stalin and the USSR, and so when the USSR used the Molotov/VonRibbentrob pact as a cover to anex Poland and Eastern Europe, Communist activist groups became pacifist groups in the US. Prior to the pact, many Communist fronts in the US were actively lobbying the US government to get involved in Europe, as the Spanish Civil War had turned against Spanish communists for Francisco Franco.
