Final answer:
As a southern slave owner, discovering that a friend or neighbor worked for the Underground Railroad would be angering because it represented a direct theft of property and economic resources, due to the escape of slaves that were considered the owner's property.
Step-by-step explanation:
If you were a southern slave owner, you would likely be angered to learn that your friend or neighbor worked for the Underground Railroad because it would mean they were stealing from you. The Underground Railroad was a network of routes and safe houses that enabled enslaved African Americans to escape to free states and Canada. As a slave owner, discovering participation in this network by someone close to you would be seen as a direct threat to your property and economic interests since the system of slavery was deeply intertwined with the Southern economy.
Supporting the Underground Railroad was viewed as undermining the institution of slavery, which held significant social and economic power in the South. The act of aiding slaves to escape was illegal and punishable, and as a result, would have been considered a severe and personal betrayal, fueling anger and distrust among slaveholders.