Several of the McBride children became involved in the civil rights movement. Do you think that this was a or a combination of these factors? 
 result of the times in which they lived, their need to belong to a group that lent them a solid identity,

I think it is a combination of all the factors you mentioned. Ruth was a complex lady who was determined to pass her values onto her children. Ruth's values were firm and her insistence on education and human rights were unwavering. It is not surprising that her grown children reflect these traits.