Complex sentence: When the group arrived the owner told them that white customers would stop coming into the restaurant if blacks were served; in response, the 30 members of the group stayed until the owner agreed to allow African American patrons.
Split into simpler sentences: When the group arrived, the owner told them that white customers would stop coming into the restaurant if blacks were served. In response, the 30 members of the group stayed until the owner agreed to allow African American patrons.