His teaching of the theory of evolution lead him to be arrested, as this broke a Tennessee state law. The AFT supported him, as he was willing to challenge government interference in with the science curriculum.
If you were a supporter of slavery, you would most likely vote for Stephen A. Douglas (democratic party) in the 1858 Illinois Senate race.
The main way in which sermons differ from those of more traditional ministers is that sermons provide more of a "lecture," and speak to a specific topic that the minister feels is important.