The correct answer to this open question is the following.
If you were a proslavery advocate, how would you feel about the platform of the newly formed Republican Party?
Well, if I were a proslavery advocate, I will really be worried about the abolitionist ideas of the northerners and specifically, of the Republican Party. As an advocate of slavery, I know that as a landlord I own large plantations in the south. And this large plantation need slaves to grow crops and produce the number of crops needed to trade and be exported to Europe. Slavery is an important part of the economy of the southern states. So if Republicans want to abolish slavery, my plantation system is at high risk.