What angered the south in uncle toms cabin?

It was the fact that Uncle Tom's Cabin disapproved of the South for their dark practices of slavery that had them so upset. The book contained material that was written after examining the reality of slavery and the slaveowners, and of course, majority of South criticized the book, mainly those that owned slaves.

They didn't like Uncle Toms's Cabin because it told the harsh reality of slavery. It told that slavery was cruel and unjust. This angered southerners.