Now Charles is African American by birth, Canadian by adoption, as he'd been a Black Panther in his youth & escaped to Canada during the Viet Nam War era. I wouldn't call him a radical. I'd call him a fantasy writer. But certainly he was swept up in the times & his life was shaped more by American wars against Southeast Asians & against black America more than it was shaped by his own goodhearted decency.
There was another Charles Saunders out there, though, in England, a director active up until the 1960s, who died in his nineties a few years ago. The international movie data base thinks Charles R. Saunders is the same as Charles Saunders, & credits the crime film director of the 1950s & 1960s with having scripted Amazons (Amazonas, 1986) & a follow-up sword & sorcery film from the same Argentinian director & crew as produced by Roger Corman,Stormquest (El Ojo de la tormenta,1987) featuring Linda Lutz as the unintentionally comically deviant Stormqueen. http://www.weirdwildrealm.com/f-goldtempleamazons.html