I assume it never even occurred to the supporters of this law that just because you’re a white person doesn’t mean you automatically need to identify with the oppressors in the story instead of identifying with the people fighting against oppression. Even during the height of the Confederacy there were always some white folks doing the right thing by helping their fellow human beings escape to freedom.
Heck, here’s one they can brag about if it makes them feel better: Obadiah Bush, ancestor of the Bush political dynasty, was vice-President of the American Anti-Slavery Society and a supporter of the Underground Railroad. That’s right, Florida! Your favorite failson of a former governor had a pretty woke great-great-great-grandfather!