Who is Ruth and Marvin Kramer from The Chamber and what is their importance?

Marvin Kramer is a Jewish lawyer, who lives in Greenville, Mississippi. Ruth is his wife. Marvin works diligently to support and promote the Civil Rights Movement and becomes well known as a black sympathizer, something that attracts the notice of the KKK. Marvin is seriously injured and both of his sons are killed when a bomb set by the KKK detonates in his office.