Complex sentence: He praised the plantation owners and denied they were brutal, arguing they provided adequate food, clothing, housing, medical care and training in modern technology--that they formed a "school" which helped "civilize" the slaves.
Split into simpler sentences: He praised the plantation owners and denied they were brutal. Phillips argued that they provided adequate food, clothing, housing, medical care and training in modern technology--that they formed a "school" which helped "civilize" the slaves.