Pete Seeger is a political activist, environmentalist and a folk singer. Both men came to prominence in the 1940's. In 1944, Mr. Kramer compiled an anthology of anti-Hitler poems, ''Seven Poets in Search of an Answer,'' which included the work of Maxwell Bodenheim, Langston Hughes and Alfred Kreymborg. In 1948 Mr. Seeger and three compatriots, Lee Hays, Ronnie Gilbert and Fred Hellerman, began singing together in a quartet called the Weavers.