One of the most significant effects of rhetoric like that used here was A) widespread opposition to the Civil War. B) increased support for westward expansion. C) the demise of the two-party system. D) increased sectional divisions between the North and South.

D). Increased sectional divisions between the north and south.

Explanation:

As per the question, one of the most significant impacts of rhetoric similar to here is the 'increased sectional divisions between the north and south' as it convinces people through using an effective and persuasive language.  In the given excerpt, the language adopted by the speaker invokes the audience to believe that 'it is a great and dangerous error to suppose that all people are equally entitled to liberty.'

The claim is logically supplemented by various rhetoric tools(in the language) that convinced the people that 'liberty is a reward to be earned, not a blessing to be gratuitously lavished... people too ignorant, degraded and vicious to be capable either of appreciating or of enjoying it.' Thus, the language like this contributed to encourage the widening of the rift between the north and south. Therefore, option D is the correct answer.