Yes, it is absolutely ridiculous that slave patrols existed and formed the basis for later police departments in the south. It is also ridiculous that labor-busting squads existed in the north, which formed the basis for later police departments in the north.
The history is there, it is what it is, as ridiculous as that is. You might argue that modern police have far outgrown their origins, and then it would be up to readers to decide which whether your claim is also ridiculous, given how many police departments generally exhibit qualities consonant with their origins.